CVE-2024-5535

Description

Issue summary: Calling the OpenSSL API function SSL_select_next_proto with an empty supported client protocols buffer may cause a crash or memory contents to be sent to the peer. Impact summary: A buffer overread can have a range of potential consequences such as unexpected application beahviour or a crash. In particular this issue could result in up to 255 bytes of arbitrary private data from memory being sent to the peer leading to a loss of confidentiality. However, only applications that directly call the SSL_select_next_proto function with a 0 length list of supported client protocols are affected by this issue. This would normally never be a valid scenario and is typically not under attacker control but may occur by accident in the case of a configuration or programming error in the calling application. The OpenSSL API function SSL_select_next_proto is typically used by TLS applications that support ALPN (Application Layer Protocol Negotiation) or NPN (Next Protocol Negotiation). NPN is older, was never standardised and is deprecated in favour of ALPN. We believe that ALPN is significantly more widely deployed than NPN. The SSL_select_next_proto function accepts a list of protocols from the server and a list of protocols from the client and returns the first protocol that appears in the server list that also appears in the client list. In the case of no overlap between the two lists it returns the first item in the client list. In either case it will signal whether an overlap between the two lists was found. In the case where SSL_select_next_proto is called with a zero length client list it fails to notice this condition and returns the memory immediately following the client list pointer (and reports that there was no overlap in the lists). This function is typically called from a server side application callback for ALPN or a client side application callback for NPN. In the case of ALPN the list of protocols supplied by the client is guaranteed by libssl to never be zero in length. The list of server protocols comes from the application and should never normally be expected to be of zero length. In this case if the SSL_select_next_proto function has been called as expected (with the list supplied by the client passed in the client/client_len parameters), then the application will not be vulnerable to this issue. If the application has accidentally been configured with a zero length server list, and has accidentally passed that zero length server list in the client/client_len parameters, and has additionally failed to correctly handle a "no overlap" response (which would normally result in a handshake failure in ALPN) then it will be vulnerable to this problem. In the case of NPN, the protocol permits the client to opportunistically select a protocol when there is no overlap. OpenSSL returns the first client protocol in the no overlap case in support of this. The list of client protocols comes from the application and should never normally be expected to be of zero length. However if the SSL_select_next_proto function is accidentally called with a client_len of 0 then an invalid memory pointer will be returned instead. If the application uses this output as the opportunistic protocol then the loss of confidentiality will occur. This issue has been assessed as Low severity because applications are most likely to be vulnerable if they are using NPN instead of ALPN - but NPN is not widely used. It also requires an application configuration or programming error. Finally, this issue would not typically be under attacker control making active exploitation unlikely. The FIPS modules in 3.3, 3.2, 3.1 and 3.0 are not affected by this issue. Due to the low severity of this issue we are not issuing new releases of OpenSSL at this time. The fix will be included in the next releases when they become available.

Overview

State: PUBLISHED
Assigner (CNA): openssl
CVSS severity: CRITICAL
CVSS score: 9.1 / 10
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Effective score: 9.1 / 10 CRITICAL source: CNA overview
MSRC score: 9.1 / 10 CRITICAL MS rating: Important · Remote Code Execution
CWE(s): CWE-125
Reserved: 2024-05-30
Published: 2024-06-27 12:30 UTC
Last updated: 2026-05-12 13:35 UTC
Source: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2024/5xxx/CVE-2024-5535.json
Linked Threat: CVE-2024-5535 — Informational Bulletin: Impact of OpenSSL Vulnerabilities CVE-2024-5535 and CVE-2024-6119

NVD triage scoring NVD CVE 2.0

Layer NVD adds on top of the CNA's CVE record — published / last-modified timestamps, exploitability / impact subscores, and the FIRST.org EPSS probability that this CVE will be exploited in the wild in the next 30 days.

NVD published: 2024-06-27 11:15:24 UTC
NVD last modified: 2026-06-17 08:16:08 UTC
NVD CVSS v3.1: 9.1 / 10 CRITICAL source: 134c704f-9b21-4f2e-91b3-4a467353bcc0
NVD CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Exploitability subscore: 3.9 / 10
Impact subscore: 5.2 / 10
EPSS score: 0.0558 (probability of exploitation in next 30 days)
EPSS percentile: 92.06% vs all CVEs — higher = more likely to be exploited, as of 2026-07-26

European Union Vulnerability Database ENISA EUVD

ENISA's official EU repository for curated vulnerability intelligence. Carries a separate identifier (EUVD-YYYY-NNNN) and frequently exposes an earlier-published description + CVSS than NVD does.

EUVD ID: EUVD-2024-46737
Assigner: openssl
Published: Jun 27, 2024, 10:30:53 AM
Updated: May 12, 2026, 11:35:07 AM
EUVD base score (CVSS 3.1): 9.1 / 10
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
EUVD-reported EPSS: 6.8700
Vendors: OpenSSL
Products: OpenSSL (1.1.1 <1.1.1za)

OpenSSL (3.1.0 <3.1.7)

OpenSSL (3.2.0 <3.2.3)

OpenSSL (1.0.2 <1.0.2zk)

OpenSSL (3.0.0 <3.0.15)

OpenSSL (3.3.0 <3.3.2)
Aliases: GHSA-4fc7-mvrr-wv2c

ENISA description: Issue summary: Calling the OpenSSL API function SSL_select_next_proto with an empty supported client protocols buffer may cause a crash or memory contents to be sent to the peer. Impact summary: A buffer overread can have a range of potential consequences such as unexpected application beahviour or a crash. In particular this issue could result in up to 255 bytes of arbitrary private data from memory being sent to the peer leading to a loss of confidentiality. However, only applications that directly call the SSL_select_next_proto function with a 0 length list of supported client protocols are affected by this issue. This would normally never be a valid scenario and is typically not under attacker control but may occur by accident in the case of a configuration or programming error in the calling application. The OpenSSL API function SSL_select_next_proto is typically used by TLS applications that support ALPN (Application Layer Protocol Negotiation) or NPN (Next Protocol Negotiation). NPN is older, was never standardised and is deprecated in favour of ALPN. We believe that ALPN is significantly more widely deployed than NPN. The SSL_select_next_proto function accepts a list of protocols from the server and a list of protocols from the client and returns the first protocol that appears in the server list that also appears in the client list. In the case of no overlap between the two lists it returns the first item in the client list. In either case it will signal whether an overlap between the two lists was found. In the case where SSL_select_next_proto is called with a zero length client list it fails to notice this condition and returns the memory immediately following the client list pointer (and reports that there was no overlap in the lists). This function is typically called from a server side application callback for ALPN or a client side application callback for NPN. In the case of ALPN the list of protocols supplied by the client is guaranteed by libssl to never be zero in length. The list of server protocols comes from the application and should never normally be expected to be of zero length. In this case if the SSL_select_next_proto function has been called as expected (with the list supplied by the client passed in the client/client_len parameters), then the application will not be vulnerable to this issue. If the application has accidentally been configured with a zero length server list, and has accidentally passed that zero length server list in the client/client_len parameters, and has additionally failed to correctly handle a "no overlap" response (which would normally result in a handshake failure in ALPN) then it will be vulnerable to this problem. In the case of NPN, the protocol permits the client to opportunistically select a protocol when there is no overlap. OpenSSL returns the first client protocol in the no overlap case in support of this. The list of client protocols comes from the application and should never normally be expected to be of zero length. However if the SSL_select_next_proto function is accidentally called with a client_len of 0 then an invalid memory pointer will be returned instead. If the application uses this output as the opportunistic protocol then the loss of confidentiality will occur. This issue has been assessed as Low severity because applications are most likely to be vulnerable if they are using NPN instead of ALPN - but NPN is not widely used. It also requires an application configuration or programming error. Finally, this issue would not typically be under attacker control making active exploitation unlikely. The FIPS modules in 3.3, 3.2, 3.1 and 3.0 are not affected by this issue. Due to the low severity of this issue we are not issuing new releases of OpenSSL at this time. The fix will be included in the next releases when they become available.

EUVD references (7)

Microsoft Security Response Center MSRC

Microsoft's vendor-authoritative record from the Security Update Guide — its own CVSS score, impact, severity rating, exploit assessment, and KB-article fixes. Refreshed 2026-08-12 01:06 UTC (source: CVRF).

MS severity: Important
Impact: Remote Code Execution
MS CVSS base score: 9.1 / 10 (temporal 8.7)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H/RL:O/RC:C
Exploit assessment: Publicly Disclosed:No;Exploited:No;Latest Software Release:Exploitation Less Likely
Release: 2024-Nov

Microsoft remediations / KB articles (6)

openssl — Vendor Fix / CBL-Mariner (fixed build 3.3.0-2)
https://nvd.nist.gov/vuln/detail/CVE-2024-5535 — None Available / openssl
cloud-hypervisor-cvm — Vendor Fix / CBL-Mariner (fixed build 38.0.72.2-3)
Release Notes — Vendor Fix / Security Update (fixed build 1.0.7001.0101)
https://docs.microsoft.com/en-us/microsoft-365/security/defender-endpoint/mtd?view=o365-worldwide — None Available / Release Notes
https://docs.microsoft.com/en-us/microsoft-365/security/defender-endpoint/mac-updates?view=o365-worldwide — None Available / Release Notes

Microsoft FAQ (1)

How could an attacker exploit this vulnerability?

Exploitation of this vulnerability requires that an attacker send a malicious link to the victim via email, or that they convince the user to click the link, typically by way of an enticement in an email or Instant Messenger message. In the worst-case email attack scenario, an attacker could send a specially crafted email to the user without a requirement that the victim open, read, or click on the link. This could result in the attacker executing remote code on the victim's machine. When multiple attack vectors can be used, we assign a score based on the scenario with the higher risk (UI:N).

Affected products (1)

Vendor	Product	Versions	Platforms
OpenSSL	OpenSSL	`3.3.0` (affected), `3.2.0` (affected), `3.1.0` (affected), `3.0.0` (affected), `1.1.1` (affected), `1.0.2` (affected)	—

Vendor references (7)

References embedded in the original CVE record by the assigning CNA.

MITRE references (7) cveawg.mitre.org

Pulled from MITRE's CVE Services API by the 🛰 Backfill from MITRE button.

Web references (24)

DuckDuckGo results ranked by threat-intel / vendor advisory domains. Generated by the 🔎 Find references (web) button above — same flow as the Remediations search.

None Available msrc
None Available msrc
MSRC update guide: CVE-2024-5535 msrc
None Available msrc
https://aix.software.ibm.com/aix/efixes/security/python_advisory17.asc rapid7:aix.software.ibm.com
https://aix.software.ibm.com/aix/efixes/security/openssl_advisory42.asc rapid7:aix.software.ibm.com
https://security.alpinelinux.org/vuln/CVE-2024-5535 rapid7:security.alpinelinux.org
https://errata.rockylinux.org/RLSA-2025:1673 rapid7:errata.rockylinux.org
https://errata.rockylinux.org/RLSA-2024:7848 rapid7:errata.rockylinux.org
https://errata.rockylinux.org/RLSA-2024:9333 rapid7:errata.rockylinux.org
https://errata.rockylinux.org/RLSA-2025:1671 rapid7:errata.rockylinux.org
https://errata.almalinux.org/8/ALSA-2025-1673.html rapid7:errata.almalinux.org
https://errata.almalinux.org/8/ALSA-2024-7848.html rapid7:errata.almalinux.org
https://errata.almalinux.org/9/ALSA-2024-9333.html rapid7:errata.almalinux.org
https://errata.almalinux.org/9/ALSA-2025-1671.html rapid7:errata.almalinux.org
https://alas.aws.amazon.com/AL2023/ALAS-2024-677.html rapid7:alas.aws.amazon.com
https://www.dell.com/support/kbdoc/en-us/000278110/dsa-2025-050-dell-powerstore-x-security-update-for-multiple-vulnerabilities rapid7:www.dell.com
https://www.dell.com/support/kbdoc/en-us/000261519/dsa-2024-497-dell-powerstore-t-security-update-for-multiple-vulnerabilities rapid7:www.dell.com
https://www.dell.com/support/kbdoc/en-us/000250483/dsa-2024-462-dell-powerstore-t-security-update-for-multiple-vulnerabilities rapid7:www.dell.com
https://euvd.enisa.europa.eu/vulnerability/EUVD-2024-46737 rapid7:euvd.enisa.europa.eu
https://attackerkb.com/topics/CVE-2024-5535 rapid7:attackerkb.com
http://cwe.mitre.org/data/definitions/125.html rapid7:cwe.mitre.org
https://www.cve.org/CVERecord?id=CVE-2024-5535 rapid7:www.cve.org
https://www.dell.com/support/kbdoc/en-us/000335103/dsa-2025-255-security-update-for-dell-poweredge-t40-mini-tower-server-for-multiple-ami-bios-vulnerabilities rapid7:www.dell.com

NVD-tagged references (28)

Reference list NVD curates from the CNA record, vendor advisories, and third-party reports. The tag chips below are NVD's analyst-assigned categories.

http://www.openwall.com/lists/oss-security/2024/06/27/1 af854a3a-2127-422b-91ae-364da2661108
http://www.openwall.com/lists/oss-security/2024/06/28/4 af854a3a-2127-422b-91ae-364da2661108
http://www.openwall.com/lists/oss-security/2024/08/15/1 af854a3a-2127-422b-91ae-364da2661108
https://cert-portal.siemens.com/productcert/html/ssa-265688.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
https://cert-portal.siemens.com/productcert/html/ssa-277137.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
https://cert-portal.siemens.com/productcert/html/ssa-398330.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
https://cert-portal.siemens.com/productcert/html/ssa-613116.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
https://cert-portal.siemens.com/productcert/html/ssa-769027.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
https://cert-portal.siemens.com/productcert/html/ssa-915275.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
https://github.com/openssl/openssl/commit/4ada436a1946cbb24db5ab4ca082b69c1bc10f37 openssl-security@openssl.org
https://github.com/openssl/openssl/commit/4ada436a1946cbb24db5ab4ca082b69c1bc10f37 af854a3a-2127-422b-91ae-364da2661108
https://github.com/openssl/openssl/commit/99fb785a5f85315b95288921a321a935ea29a51e openssl-security@openssl.org
https://github.com/openssl/openssl/commit/99fb785a5f85315b95288921a321a935ea29a51e af854a3a-2127-422b-91ae-364da2661108
https://github.com/openssl/openssl/commit/cf6f91f6121f4db167405db2f0de410a456f260c openssl-security@openssl.org
https://github.com/openssl/openssl/commit/cf6f91f6121f4db167405db2f0de410a456f260c af854a3a-2127-422b-91ae-364da2661108
https://github.com/openssl/openssl/commit/e86ac436f0bd54d4517745483e2315650fae7b2c openssl-security@openssl.org
https://github.com/openssl/openssl/commit/e86ac436f0bd54d4517745483e2315650fae7b2c af854a3a-2127-422b-91ae-364da2661108
https://github.openssl.org/openssl/extended-releases/commit/9947251413065a05189a63c9b7a6c1d4e224c21c openssl-security@openssl.org
https://github.openssl.org/openssl/extended-releases/commit/9947251413065a05189a63c9b7a6c1d4e224c21c af854a3a-2127-422b-91ae-364da2661108
https://github.openssl.org/openssl/extended-releases/commit/b78ec0824da857223486660177d3b1f255c65d87 openssl-security@openssl.org
https://github.openssl.org/openssl/extended-releases/commit/b78ec0824da857223486660177d3b1f255c65d87 af854a3a-2127-422b-91ae-364da2661108
https://lists.debian.org/debian-lts-announce/2024/10/msg00033.html af854a3a-2127-422b-91ae-364da2661108
https://lists.debian.org/debian-lts-announce/2024/11/msg00000.html af854a3a-2127-422b-91ae-364da2661108
https://security.netapp.com/advisory/ntap-20240712-0005/ af854a3a-2127-422b-91ae-364da2661108
https://security.netapp.com/advisory/ntap-20241025-0006/ af854a3a-2127-422b-91ae-364da2661108
https://security.netapp.com/advisory/ntap-20241025-0010/ af854a3a-2127-422b-91ae-364da2661108
https://www.openssl.org/news/secadv/20240627.txt openssl-security@openssl.org
https://www.openssl.org/news/secadv/20240627.txt af854a3a-2127-422b-91ae-364da2661108

Indicators (1)

IOCs linked to the auto-promoted Threat row.

Type	Value	VirusTotal	Attached
cve	`CVE-2024-5535`	no local data	2026-05-14 09:34 UTC

Remediations (15)

Remediations are stored against the linked Threat row; the list below is deduplicated across both pages.

RHSA-2024:5535 - Security Advisory - Red Hat Customer Portal

web:access.redhat.com

Security Fix (es): python: Path traversal on tempfile.TemporaryDirectory ( CVE -2023-6597) For more details about the security issue (s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page (s) listed in the References section.

2026-05-23 10:49 UTC
CVE-2024-5535 - SSL_select_next_proto buffer overread

web:cvefeed.io

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2024-5535 weaknesses.

2026-05-23 10:49 UTC
CVE-2024-5535 - Exploits & Severity - Feedly

web:feedly.com

CVE-2024-5535 is a low severity vulnerability in OpenSSL that allows for a buffer overread when calling the SSL_select_next_proto function with an empty supported client protocols buffer.

2026-05-23 10:49 UTC
Nvd - Cve-2024-5535

web:nvd.nist.gov

Secure .gov websites use HTTPS A lock () or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

2026-05-23 10:49 UTC
Security Update Guide - Microsoft

web:portal.msrc.microsoft.com

The Security Update Guide provides information on the latest Microsoft security updates, helping users understand and address potential vulnerabilities effectively.

2026-05-23 10:49 UTC
CVE Record: CVE-2024-5535

web:www.cve.org

Description Issue summary: Calling the OpenSSL API function SSL_select_next_proto with an empty supported client protocols buffer may cause a crash or memory contents to be sent to the peer. Impact summary: A buffer overread can have a range of potential consequences such as unexpected application beahviour or a crash. In particular this issue could result in up to 255 bytes of arbitrary ...

2026-05-23 10:49 UTC
Oracle Critical Patch Update Advisory - October 2025

web:www.oracle.com

This Critical Patch Update contains 374 new security patches across the product families listed below. Please note that an MOS note summarizing the content of this Critical Patch Update and other Oracle Software Security Assurance activities is located at October 2025 Critical Patch Update: Executive Summary and Analysis.

2026-05-23 10:49 UTC
CVE-2024-5535 Common Vulnerabilities and Exposures | SUSE

web:www.suse.com

Secure your Linux systems from CVE-2024-5535 . Stay ahead of potential threats with the latest security updates from SUSE.

2026-05-23 10:49 UTC
CVE-2024-5535 | Tenable®

web:www.tenable.com

Issue summary: Calling the OpenSSL API function SSL_select_next_proto with an empty supported client protocols buffer may cause a crash or memory contents to be sent to the peer. Impact summary: A buffer overread can have a range of potential consequences such as unexpected application beahviour or a crash. In particular this issue could result in up to 255 bytes of arbitrary private data from ...

2026-05-23 10:49 UTC
Patch Tuesday May 2026: Security Updates & CVE Analysis

web:zecurit.com

Get the complete breakdown of Microsoft's May 2026 Patch Tuesday. We analyze the latest security updates and all critical CVEs .

2026-05-23 10:49 UTC
CVE-2024-5535 - Vulnerability Details - OpenCVE

web:app.opencve.io

Finally, this issue would not typically be under attacker control making active exploitation unlikely. The FIPS modules in 3.3, 3.2, 3.1 and 3.0 are not affected by this issue. Due to the low severity of this issue we are not issuing new releases of OpenSSL at this time. The fix will be included in the next releases when they become available.

2026-05-17 11:55 UTC
CVE-2024-5535 | Ubuntu

web:ubuntu.com

Ubuntu is an open source software operating system that runs from the desktop, to the cloud, to all your internet connected things.

2026-05-17 11:55 UTC
DSA-2025-075: Security Update for Dell Data Protection Advisor for ...

web:www.dell.com

Dell Data Protection Advisor remediation is available for multiple vulnerabilities that could be exploited by malicious users to compromise the affected system.

2026-05-17 11:55 UTC
Oracle Critical Patch Update Advisory - July 2025

web:www.oracle.com

Oracle Critical Patch Update Advisory - July 2025 Description A Critical Patch Update is a collection of patches for multiple security vulnerabilities. These patches address vulnerabilities in Oracle code and in third party components included in Oracle products. These patches are usually cumulative, but each advisory describes only the security patches added since the previous Critical Patch ...

2026-05-17 11:55 UTC
CVE-2024-5535: OpenSSL Information Disclosure Vulnerability

web:www.sentinelone.com

CVE-2024-5535 is an information disclosure vulnerability in OpenSSL's SSL_select_next_proto function. Learn about its impact, affected versions, and mitigation .

2026-05-17 11:55 UTC

AI Forensic Analysis

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Raw JSON

The full cvelistV5 record. Download as CVE-2024-5535.json.

{
  "containers": {
    "adp": [
      {
        "affected": [
          {
            "cpes": [
              "cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*"
            ],
            "defaultStatus": "unknown",
            "product": "openssl",
            "vendor": "openssl",
            "versions": [
              {
                "lessThan": "3.3.2",
                "status": "affected",
                "version": "3.3.0",
                "versionType": "custom"
              },
              {
                "lessThan": "3.2.3",
                "status": "affected",
                "version": "3.2.0",
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              },
              {
                "lessThan": "3.1.7",
                "status": "affected",
                "version": "3.1.0",
                "versionType": "custom"
              },
              {
                "lessThan": "3.0.15",
                "status": "affected",
                "version": "3.0.0",
                "versionType": "custom"
              },
              {
                "lessThan": "1.1.1za",
                "status": "affected",
                "version": "1.1.1",
                "versionType": "custom"
              },
              {
                "lessThan": "1.0.2zk",
                "status": "affected",
                "version": "1.0.2",
                "versionType": "custom"
              }
            ]
          }
        ],
        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "LOW",
              "attackVector": "NETWORK",
              "availabilityImpact": "HIGH",
              "baseScore": 9.1,
              "baseSeverity": "CRITICAL",
              "confidentialityImpact": "HIGH",
              "integrityImpact": "NONE",
              "privilegesRequired": "NONE",
              "scope": "UNCHANGED",
              "userInteraction": "NONE",
              "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H",
              "version": "3.1"
            }
          },
          {
            "other": {
              "content": {
                "id": "CVE-2024-5535",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2024-11-08T00:00:00+00:00",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2024-11-14T04:55:17.007Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      },
      {
        "providerMetadata": {
          "dateUpdated": "2025-11-03T22:32:30.900Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "name": "OpenSSL Advisory",
            "tags": [
              "vendor-advisory",
              "x_transferred"
            ],
            "url": "https://www.openssl.org/news/secadv/20240627.txt"
          },
          {
            "name": "3.3.2 git commit",
            "tags": [
              "patch",
              "x_transferred"
            ],
            "url": "https://github.com/openssl/openssl/commit/e86ac436f0bd54d4517745483e2315650fae7b2c"
          },
          {
            "name": "3.2.3 git commit",
            "tags": [
              "patch",
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              "value": "Issue summary: Calling the OpenSSL API function SSL_select_next_proto with an<br>empty supported client protocols buffer may cause a crash or memory contents to<br>be sent to the peer.<br><br>Impact summary: A buffer overread can have a range of potential consequences<br>such as unexpected application beahviour or a crash. In particular this issue<br>could result in up to 255 bytes of arbitrary private data from memory being sent<br>to the peer leading to a loss of confidentiality. However, only applications<br>that directly call the SSL_select_next_proto function with a 0 length list of<br>supported client protocols are affected by this issue. This would normally never<br>be a valid scenario and is typically not under attacker control but may occur by<br>accident in the case of a configuration or programming error in the calling<br>application.<br><br>The OpenSSL API function SSL_select_next_proto is typically used by TLS<br>applications that support ALPN (Application Layer Protocol Negotiation) or NPN<br>(Next Protocol Negotiation). NPN is older, was never standardised and<br>is deprecated in favour of ALPN. We believe that ALPN is significantly more<br>widely deployed than NPN. The SSL_select_next_proto function accepts a list of<br>protocols from the server and a list of protocols from the client and returns<br>the first protocol that appears in the server list that also appears in the<br>client list. In the case of no overlap between the two lists it returns the<br>first item in the client list. In either case it will signal whether an overlap<br>between the two lists was found. In the case where SSL_select_next_proto is<br>called with a zero length client list it fails to notice this condition and<br>returns the memory immediately following the client list pointer (and reports<br>that there was no overlap in the lists).<br><br>This function is typically called from a server side application callback for<br>ALPN or a client side application callback for NPN. In the case of ALPN the list<br>of protocols supplied by the client is guaranteed by libssl to never be zero in<br>length. The list of server protocols comes from the application and should never<br>normally be expected to be of zero length. In this case if the<br>SSL_select_next_proto function has been called as expected (with the list<br>supplied by the client passed in the client/client_len parameters), then the<br>application will not be vulnerable to this issue. If the application has<br>accidentally been configured with a zero length server list, and has<br>accidentally passed that zero length server list in the client/client_len<br>parameters, and has additionally failed to correctly handle a \"no overlap\"<br>response (which would normally result in a handshake failure in ALPN) then it<br>will be vulnerable to this problem.<br><br>In the case of NPN, the protocol permits the client to opportunistically select<br>a protocol when there is no overlap. OpenSSL returns the first client protocol<br>in the no overlap case in support of this. The list of client protocols comes<br>from the application and should never normally be expected to be of zero length.<br>However if the SSL_select_next_proto function is accidentally called with a<br>client_len of 0 then an invalid memory pointer will be returned instead. If the<br>application uses this output as the opportunistic protocol then the loss of<br>confidentiality will occur.<br><br>This issue has been assessed as Low severity because applications are most<br>likely to be vulnerable if they are using NPN instead of ALPN - but NPN is not<br>widely used. It also requires an application configuration or programming error.<br>Finally, this issue would not typically be under attacker control making active<br>exploitation unlikely.<br><br>The FIPS modules in 3.3, 3.2, 3.1 and 3.0 are not affected by this issue.<br><br>\n\nDue to the low severity of this issue we are not issuing new releases of<br>OpenSSL at this time. The fix will be included in the next releases when they<br>become available."
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