CVE-2026-99283

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: conntrack: tcp: use UNACK timeout for non-closing RST packets Commit be0502a3f2e9 ("netfilter: conntrack: tcp: only close if RST matches exact sequence") keeps an established conntrack entry in ESTABLISHED when an in-window RST does not match the expected sequence number exactly, so the endpoint can validate the RST with a challenge ACK. The timeout selection nevertheless uses the CLOSE timeout for every RST packet. The bug is that timeout selection is based on the packet type, not on the state transition result: even when RST validation keeps new_state in ESTABLISHED, the timeout is still forced to TCP_CONNTRACK_CLOSE. Linux TCP independently rate limits challenge ACKs per socket. A second non-exact RST can therefore arrive after the first challenge ACK has restored the timeout but before the rate limit expires. The second RST lowers the timeout to 10 seconds again while the endpoint suppresses the second challenge ACK, allowing the conntrack entry to expire while both TCP endpoints remain established. Using the ESTABLISHED timeout for such RSTs would avoid this short expiration window, but it could also retain stale entries for the five-day default because conntrack cannot reliably match the endpoint's exact TCP state. Use the UNACK timeout for RST packets that leave the conntrack entry in TCP_CONNTRACK_ESTABLISHED. Exact-match RSTs and accepted RST packet trains still fall through to timeouts[new_state], which preserves the CLOSE timeout when conntrack accepts the RST as closing the flow. This avoids the aggressive 10-second expiration window for non-exact RSTs while preserving the short timeout for RSTs that conntrack accepts as closing the flow.

Overview

State: PUBLISHED
Assigner (CNA): Linux
CVSS severity: —
CVSS score: —
CVSS vector: —
Effective score: no score available from CNA, NVD, or AI yet
CWE(s): —
Reserved: 2026-09-25
Published: 2026-11-07 20:14 UTC
Last updated: 2026-11-07 20:14 UTC
Source: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/99xxx/CVE-2026-99283.json

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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-2026-119327

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Affected products (2)

Vendor	Product	Versions	Platforms
Linux	Linux	`1da177e4c3f41524e886b7f1b8a0c1fc7321cac2` (affected), `1da177e4c3f41524e886b7f1b8a0c1fc7321cac2` (affected), `0` (affected)	—
Linux	Linux	`6.18.61` (unaffected), `7.3` (unaffected)	—

Vendor references (2)

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

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.

Remediations (10)

October 2026 Critical Patch Update Released | security

web:blogs.oracle.com

For more information about the Critical Patch Update program, see the security vulnerability remediation practices page located on the Oracle Trust Center.

2026-11-08 11:05 UTC
CVE Database Search & Remediation Guidance

web:cvedatabase.com

Search and analyze CVE vulnerabilities with instant access to CVSS scores, affected products, and remediation guidance.

2026-11-08 11:05 UTC
CISA Requires Federal Agencies to Patch Critical Vulnerabilities Within ...

web:cybersecuritynews.com

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has issued Binding Operational Directive (BOD) 26-04, titled "Prioritizing Security Updates Based on Risk," compelling all Federal Civilian Executive Branch (FCEB) agencies to remediate the most dangerous known exploited vulnerabilities within just three calendar days.

2026-11-08 11:05 UTC
NVD - Search

web:nvd.nist.gov

Search Please make use of the interactive search interfaces to find information in the database!

2026-11-08 11:05 UTC
SAP Security Patch Day - October 2026

web:support.sap.com

On 13 th of October 2026 , SAP security patch day saw the release of 16 new security notes and 4 GitHub security advisories. There are 2 updates to previously released security notes.

2026-11-08 11:05 UTC
CVE-2026-99283 - Linux Kernel Netfilter Conntrack Timeout…

web:vulmon.com

Vulnerability Summary A vulnerability in Linux kernel's netfilter conntrack component allows for premature expiration of established TCP connections. This occurs when a non-closing RST packet does not exactly match the expected sequence number, leading to an incorrect timeout selection. The system incorrectly applies a close timeout instead of an established timeout, potentially reducing the ...

2026-11-08 11:05 UTC
CVE-2026-99283 - vulnerability database | Vulners.com

web:vulners.com

CVE-2026-99283 🗓️ 07 Nov 2026 12:14:11 Reported by Linux Type cve 🔗 web.nvd.nist.gov 👁 11 Views

2026-11-08 11:05 UTC
What Is CVE Remediation in 2026? - aikido.dev

web:www.aikido.dev

CVE remediation is fixing known flaws in the software you run. Why upgrading often fails, what remediation actually involves, and how backporting fixes it.

2026-11-08 11:05 UTC
National Vulnerability Database | NIST

web:www.nist.gov

NIST maintains the National Vulnerability Database (NVD), a repository of information on software and hardware flaws that can compromise computer security. This is a key piece of the nation's cybersecurity infrastructure.

2026-11-08 11:05 UTC
Oracle Critical Security Patch Update Advisory - September 2026

web:www.oracle.com

Prior Critical Patch Update and Critical Security Patch Update advisories should be reviewed for information regarding earlier published security patches. Refer to Critical Patch Updates, Critical Security Patch Updates, Security Alerts and Bulletins for information about Oracle Security advisories.

2026-11-08 11:05 UTC

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Raw JSON

The full cvelistV5 record. Download as CVE-2026-99283.json.

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/netfilter/nf_conntrack_proto_tcp.c"
          ],
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          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "0c6d33329960b2d884a399196c8403643d8a9de6",
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              "versionType": "git"
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              "versionType": "git"
            },
            {
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            }
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          "vendor": "Linux",
          "versions": [
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              "lessThanOrEqual": "6.18.*",
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            },
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              "versionType": "original_commit_for_fix"
            }
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: conntrack: tcp: use UNACK timeout for non-closing RST packets\n\nCommit be0502a3f2e9 (\"netfilter: conntrack: tcp: only close if RST\nmatches exact sequence\") keeps an established conntrack entry in\nESTABLISHED when an in-window RST does not match the expected sequence\nnumber exactly, so the endpoint can validate the RST with a challenge\nACK.\n\nThe timeout selection nevertheless uses the CLOSE timeout for every RST\npacket.  The bug is that timeout selection is based on the packet type,\nnot on the state transition result: even when RST validation keeps\nnew_state in ESTABLISHED, the timeout is still forced to\nTCP_CONNTRACK_CLOSE.\n\nLinux TCP independently rate limits challenge ACKs per socket.  A second\nnon-exact RST can therefore arrive after the first challenge ACK has\nrestored the timeout but before the rate limit expires.  The second RST\nlowers the timeout to 10 seconds again while the endpoint suppresses the\nsecond challenge ACK, allowing the conntrack entry to expire while both\nTCP endpoints remain established.\n\nUsing the ESTABLISHED timeout for such RSTs would avoid this short\nexpiration window, but it could also retain stale entries for the\nfive-day default because conntrack cannot reliably match the endpoint's\nexact TCP state.\n\nUse the UNACK timeout for RST packets that leave the conntrack entry in\nTCP_CONNTRACK_ESTABLISHED.  Exact-match RSTs and accepted RST packet\ntrains still fall through to timeouts[new_state], which preserves the\nCLOSE timeout when conntrack accepts the RST as closing the flow.\n\nThis avoids the aggressive 10-second expiration window for non-exact\nRSTs while preserving the short timeout for RSTs that conntrack accepts\nas closing the flow."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-11-07T20:14:11.433Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/0c6d33329960b2d884a399196c8403643d8a9de6"
        },
        {
          "url": "https://git.kernel.org/stable/c/bf80e6802273a900311b44e47c9b1a59c6d2473c"
        }
      ],
      "title": "netfilter: conntrack: tcp: use UNACK timeout for non-closing RST packets",
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-99283",
    "datePublished": "2026-11-07T20:14:11.433Z",
    "dateReserved": "2026-09-25T10:25:14.405Z",
    "dateUpdated": "2026-11-07T20:14:11.433Z",
    "state": "PUBLISHED"
  },
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}