CVE-2026-73548

Description

Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.36.10, 1.37.6, 1.38.4, and 1.39.1, Envoy forwards data for a configured non-WebSocket HTTP upgrade before the upstream accepts the upgrade. An unauthenticated HTTP/2 client can place a complete HTTP/1.1 request in extended CONNECT data; Envoy downgrades the request, writes the data unframed to a keep-alive HTTP/1.1 upstream, and returns the socket to the shared pool while the smuggled response remains queued. A different downstream client can then receive the attacker's response. The relevant scope boundary is that webSocket upgrades, plain CONNECT, disabled backend keep-alive, per-downstream pools, and max_requests_per_connection set to 1 are not affected by the demonstrated path. This issue is fixed in versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1.

Overview

State: PUBLISHED
Assigner (CNA): GitHub_M
CVSS severity: HIGH
CVSS score: 7.5 / 10
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Effective score: 7.5 / 10 HIGH source: CNA overview
CWE(s): CWE-444
Reserved: 2026-08-12
Published: 2026-09-21 19:35 UTC
Last updated: 2026-09-21 19:35 UTC
Source: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/73xxx/CVE-2026-73548.json
Linked Threat: CVE-2026-73548 — Envoy: Cross-user response poisoning via a generic (non-WebSocket) HTTP upgrade on Envoy's shared backend pool

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: 2026-09-21 20:17:28 UTC
NVD last modified: 2026-09-21 20:17:28 UTC
NVD CVSS v3.1: 7.5 / 10 HIGH source: security-advisories@github.com
NVD CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Exploitability subscore: 3.9 / 10
Impact subscore: 3.6 / 10

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-2026-84103
Assigner: GitHub_M
Published: Sep 21, 2026, 7:35:15 PM
Updated: Sep 21, 2026, 7:35:15 PM
EUVD base score (CVSS 3.1): 7.5 / 10
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
EUVD-reported EPSS: 0.0000
Vendors: envoyproxy
Products: envoy (< 1.36.10)

envoy (1.37.0, < 1.37.6)

envoy (1.39.0, < 1.39.1)

envoy (1.38.0, < 1.38.4)

ENISA description: Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.36.10, 1.37.6, 1.38.4, and 1.39.1, Envoy forwards data for a configured non-WebSocket HTTP upgrade before the upstream accepts the upgrade. An unauthenticated HTTP/2 client can place a complete HTTP/1.1 request in extended CONNECT data; Envoy downgrades the request, writes the data unframed to a keep-alive HTTP/1.1 upstream, and returns the socket to the shared pool while the smuggled response remains queued. A different downstream client can then receive the attacker's response. The relevant scope boundary is that webSocket upgrades, plain CONNECT, disabled backend keep-alive, per-downstream pools, and max_requests_per_connection set to 1 are not affected by the demonstrated path. This issue is fixed in versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1.

EUVD references (9)

Affected products (1)

Vendor	Product	Versions	Platforms
envoyproxy	envoy	`< 1.36.10` (affected), `>= 1.37.0, < 1.37.6` (affected), `>= 1.38.0, < 1.38.4` (affected), `>= 1.39.0, < 1.39.1` (affected)	—

Vendor references (9)

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

https://github.com/envoyproxy/envoy/security/advisories/GHSA-3vhp-c83q-jqc2 x_refsource_CONFIRM
https://github.com/envoyproxy/envoy/commit/309855626966cff176155c821043ed3b44671361 x_refsource_MISC
https://github.com/envoyproxy/envoy/commit/3c7998545a9c9fb3933a4bc1907d92f0e752bc2b x_refsource_MISC
https://github.com/envoyproxy/envoy/commit/4633b8cce3d15b8734eefe232e30c12b0140b91c x_refsource_MISC
https://github.com/envoyproxy/envoy/commit/bd6711f2617658e28dfa3df3dace6bfe3cfc0766 x_refsource_MISC
https://github.com/envoyproxy/envoy/releases/tag/v1.36.10 x_refsource_MISC
https://github.com/envoyproxy/envoy/releases/tag/v1.37.6 x_refsource_MISC
https://github.com/envoyproxy/envoy/releases/tag/v1.38.4 x_refsource_MISC
https://github.com/envoyproxy/envoy/releases/tag/v1.39.1 x_refsource_MISC

Web references (0)

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

No web references attached yet.

NVD-tagged references (9)

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

https://github.com/envoyproxy/envoy/commit/309855626966cff176155c821043ed3b44671361 security-advisories@github.com
https://github.com/envoyproxy/envoy/commit/3c7998545a9c9fb3933a4bc1907d92f0e752bc2b security-advisories@github.com
https://github.com/envoyproxy/envoy/commit/4633b8cce3d15b8734eefe232e30c12b0140b91c security-advisories@github.com
https://github.com/envoyproxy/envoy/commit/bd6711f2617658e28dfa3df3dace6bfe3cfc0766 security-advisories@github.com
https://github.com/envoyproxy/envoy/releases/tag/v1.36.10 security-advisories@github.com
https://github.com/envoyproxy/envoy/releases/tag/v1.37.6 security-advisories@github.com
https://github.com/envoyproxy/envoy/releases/tag/v1.38.4 security-advisories@github.com
https://github.com/envoyproxy/envoy/releases/tag/v1.39.1 security-advisories@github.com
https://github.com/envoyproxy/envoy/security/advisories/GHSA-3vhp-c83q-jqc2 security-advisories@github.com

Remediations (10)

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

CVE-2026-73548 | Vulnerability Database | Aqua Security

web:avd.aquasec.com

CVE-2026-73548 | | Aqua Security is the largest pure-play cloud native security company, providing customers the freedom to innovate and run their businesses with minimal friction. The Aqua Cloud Native Security Platform provides prevention, detection, and response automation across the entire application lifecycle to secure the build, secure cloud infrastructure and secure running workloads ...

2026-09-22 16:47 UTC
August 2026 cumulative update - .NET Framework | Microsoft Learn

web:learn.microsoft.com

This update installs the complete .NET Framework 3.5 product for Windows 11, version 26H1 (build version 28000) and newer. Unlike traditional cumulative updates that patch individual components, this update delivers the full .NET Framework 3.5 product as a standalone installer. It replaces any previously installed version.

2026-09-22 16:47 UTC
Security Update Guide - Microsoft

web:msrc.microsoft.com

The Microsoft Security Response Center (MSRC) investigates all reports of security vulnerabilities affecting Microsoft products and services, and provides the information here as part of the ongoing effort to help you manage security risks and help keep your systems protected.

2026-09-22 16:47 UTC
Security Update Guide - Microsoft Security Response Center

web:msrc.microsoft.com

Access Microsoft Security Response Center's guide to address vulnerabilities, manage security risks, and keep your systems protected with the latest updates.

2026-09-22 16:47 UTC
Microsoft Patch Tracker (September 2026): Exploit-Ranked | Senserva

web:senserva.com

Every Microsoft security patch (KB) and the CVEs it fixes, with severity, CVSS, and CISA KEV status. Cross-linked to the CVE reference.

2026-09-22 16:47 UTC
SAP Security Patch Day - June 2026

web:support.sap.com

SAP security Patch Day Bulletin This post shares the information on security notes that remediate vulnerabilities discovered in SAP products. SAP strongly recommends that the customer visits the support portal and applies patches on priority to protect their SAP landscape. On 9th of June 2026 , SAP security patch day saw the release of 15 new security notes.

2026-09-22 16:47 UTC
August 2026 CVE Advisory Notification - Security

web:support.servicenow.com

Due to additional analysis provided by the security researcher who discovered CVE - 2026 -6876, we have upgraded the severity rating of CVE - 2026 -6876 from High to Critical. This change affects only the severity

2026-09-22 16:47 UTC
DSA-2026-359: Security Update for Dell OpenManage Enterprise ...

web:www.dell.com

Dell OpenManage Enterprise remediation is available for multiple security vulnerabilities that may be exploited by malicious users to compromise the affected system.

2026-09-22 16:47 UTC
Oracle Critical Patch Update Advisory - July 2026

web:www.oracle.com

This Critical Patch Update contains 1448 new security patches across the product families listed below. Please note that a My Oracle Support (MOS) note summarizing the content of this Critical Patch Update and other Oracle Software Security Assurance activities is located at July 2026 Critical Patch Update: Executive Summary and Analysis.

2026-09-22 16:47 UTC
CVE-2026-73548: envoyproxy envoy: Envoy is an open source edge ... - Rapid7

web:www.rapid7.com

CVE-2026-73548 : envoyproxy envoy: Envoy is an open source edge and service proxy designed for cloud-native applications. View severity, references, and remediation details from Rapid7.

2026-09-22 16:47 UTC

AI Forensic Analysis

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Raw JSON

The full cvelistV5 record. Download as CVE-2026-73548.json.

{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "envoy",
          "vendor": "envoyproxy",
          "versions": [
            {
              "status": "affected",
              "version": "< 1.36.10"
            },
            {
              "status": "affected",
              "version": ">= 1.37.0, < 1.37.6"
            },
            {
              "status": "affected",
              "version": ">= 1.38.0, < 1.38.4"
            },
            {
              "status": "affected",
              "version": ">= 1.39.0, < 1.39.1"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.36.10, 1.37.6, 1.38.4, and 1.39.1, Envoy forwards data for a configured non-WebSocket HTTP upgrade before the upstream accepts the upgrade. An unauthenticated HTTP/2 client can place a complete HTTP/1.1 request in extended CONNECT data; Envoy downgrades the request, writes the data unframed to a keep-alive HTTP/1.1 upstream, and returns the socket to the shared pool while the smuggled response remains queued. A different downstream client can then receive the attacker's response. The relevant scope boundary is that webSocket upgrades, plain CONNECT, disabled backend keep-alive, per-downstream pools, and max_requests_per_connection set to 1 are not affected by the demonstrated path. This issue is fixed in versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "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:N",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-444",
              "description": "CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-21T19:35:15.275Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/envoyproxy/envoy/security/advisories/GHSA-3vhp-c83q-jqc2",
          "tags": [
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          ],
          "url": "https://github.com/envoyproxy/envoy/security/advisories/GHSA-3vhp-c83q-jqc2"
        },
        {
          "name": "https://github.com/envoyproxy/envoy/commit/309855626966cff176155c821043ed3b44671361",
          "tags": [
            "x_refsource_MISC"
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          "url": "https://github.com/envoyproxy/envoy/commit/309855626966cff176155c821043ed3b44671361"
        },
        {
          "name": "https://github.com/envoyproxy/envoy/commit/3c7998545a9c9fb3933a4bc1907d92f0e752bc2b",
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          "tags": [
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          ],
          "url": "https://github.com/envoyproxy/envoy/commit/4633b8cce3d15b8734eefe232e30c12b0140b91c"
        },
        {
          "name": "https://github.com/envoyproxy/envoy/commit/bd6711f2617658e28dfa3df3dace6bfe3cfc0766",
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          "url": "https://github.com/envoyproxy/envoy/commit/bd6711f2617658e28dfa3df3dace6bfe3cfc0766"
        },
        {
          "name": "https://github.com/envoyproxy/envoy/releases/tag/v1.36.10",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/envoyproxy/envoy/releases/tag/v1.36.10"
        },
        {
          "name": "https://github.com/envoyproxy/envoy/releases/tag/v1.37.6",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/envoyproxy/envoy/releases/tag/v1.37.6"
        },
        {
          "name": "https://github.com/envoyproxy/envoy/releases/tag/v1.38.4",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/envoyproxy/envoy/releases/tag/v1.38.4"
        },
        {
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          ],
          "url": "https://github.com/envoyproxy/envoy/releases/tag/v1.39.1"
        }
      ],
      "source": {
        "advisory": "GHSA-3vhp-c83q-jqc2",
        "discovery": "UNKNOWN"
      },
      "title": "Envoy: Cross-user response poisoning via a generic (non-WebSocket) HTTP upgrade on Envoy's shared backend pool"
    }
  },
  "cveMetadata": {
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    "cveId": "CVE-2026-73548",
    "datePublished": "2026-09-21T19:35:15.275Z",
    "dateReserved": "2026-08-12T20:53:46.379Z",
    "dateUpdated": "2026-09-21T19:35:15.275Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}