HighCVE-2026-31696

    Linux Kernel: security vulnerability (CVE-2026-31696)

    Published Last modified Sources: Debian LTS, Ubuntu, Siemens ProductCERT, BSI, CVE.org, EUVD, Msrc Update Guide

    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix missing validation of ticket length in non-XDR key preparsing In rxrpc_preparse(), there are two paths for parsing key payloads: the XDR path (for large payloads) and the non-XDR path (for payloads <= 28 bytes). While the XDR path (rxrpc_preparse_xdr_rxkad()) correctly validates the ticket length against AFSTOKEN_RK_TIX_MAX, the non-XDR path fails to do so.

    Update Linux Kernel to version 5.10.258, Linux Kernel to version 5.15.209, Linux Kernel to version 6.1.175.

    Affected
    • Linux Kernel lt 3.17..5.10.258
    • Linux Kernel lt 5.11..5.15.209
    • Linux Kernel lt 5.16..6.1.175
    • Linux Kernel lt 6.2..6.6.136
    • Linux Kernel lt 6.7..6.12.84
    • Linux Kernel lt 6.13..6.18.25
    • Linux Kernel lt 6.19..7.0.2
    Fixed in
    • Linux Kernel 5.10.258
    • Linux Kernel 5.15.209
    • Linux Kernel 6.1.175
    • Linux Kernel 6.6.136
    • Linux Kernel 6.12.84
    • Linux Kernel 6.18.25
    • Linux Kernel 7.0.2
    • Linux Kernel 7.1

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    7.8

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    7.8

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: Debian LTS, Ubuntu, Siemens ProductCERT, BSI, CVE.org, EUVD, Msrc Update Guide

    0.1 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 2.9

    Show all metrics
    Severity
    High
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    55.95 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    no public PoC known
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    7.8 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    7.8
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    0.1 %
    Low — model estimates < 1% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    2.9
    Low — this CVE sits in the lower 10% of all CVEs scored today.
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    —
    Published

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    In the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix missing validation of ticket length in non-XDR key preparsing In rxrpc_preparse(), there are two paths for parsing key payloads: the XDR path (for large payloads) and the non-XDR path (for payloads <= 28 bytes). While the XDR path (rxrpc_preparse_xdr_rxkad()) correctly validates the ticket length against AFSTOKEN_RK_TIX_MAX, the non-XDR path fails to do so. This allows an unprivileged user to provide a very large ticket length. When this key is later read via rxrpc_read(), the total token size (toksize) calculation results in a value that exceeds AFSTOKEN_LENGTH_MAX, triggering a WARN_ON(). [ 2001.302904] WARNING: CPU: 2 PID: 2108 at net/rxrpc/key.c:778 rxrpc_read+0x109/0x5c0 [rxrpc] Fix this by adding a check in the non-XDR parsing path of rxrpc_preparse() to ensure the ticket length does not exceed AFSTOKEN_RK_TIX_MAX, bringing it into parity with the XDR parsing logic.

    Source: Debian LTS Advisories, Ubuntu Security Notices, siemens_advisory, BSI WID Portal, BSI CSAF, NVD (NIST), ENISA EUVD, CVE.org (MITRE), cvelistv5, Microsoft Security Update Guide

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    LinuxLinux
    • 5.16 – < 6.1.175
    • 6.2 – < 6.6.136
    • 6.13 – < 6.18.25
    • 6.7 – < 6.12.84
    • 5.11 – < 5.15.209
    • 3.17 – < 5.10.258
    • —
    • 6.19 – < 7.0.2
    • 6.1.175
    • 6.6.136
    • 6.18.25
    • 6.12.84
    • 5.15.209
    • 5.10.258
    • 7.1
    • 7.0.2
    MicrosoftAzure Linux
    • azl3
    • —
    SiemensSIMATIC S7
    • 1500 TM MFP V1.1.1 GNU/Linux subsystem
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianlinuxbookworm
    Linuxdebianlinuxbullseye
    Linuxdebianlinux-6.1bullseye
    Linuxlinuxlinux_kernel7.1
    Linuxlinuxlinux_kernel—

    References & sources

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Record modifiedLinux

      Show 21 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/1fa36cf495b0023e8475d038535c05e4063211e1
      Referenceadded
      —
      https://git.kernel.org/stable/c/41a117dd80371343babc52198d1114e83eb37627
      Referenceadded
      —
      https://git.kernel.org/stable/c/4458757c020592a3094366e0fb20457383b42f92
      Referenceadded
      —
      https://git.kernel.org/stable/c/44714dfda386884919ba366411880b6fb3c3efd3
      Referenceadded
      —
      https://git.kernel.org/stable/c/9a397aa9b5e53ca63d4d6aefb542832eca389618
      Referenceadded
      —
      https://git.kernel.org/stable/c/a1be1c9ece26cea69654f28b255ff9a7906b897b
      Referenceadded
      —
      https://git.kernel.org/stable/c/ac33733b10b484d666f97688561670afd5861383
      Referenceadded
      —
      https://git.kernel.org/stable/c/ce383ba615339f8eaec646a166d2c2b015bb5ca0
      Referenceremoved
      https://git.kernel.org/stable/c/1fa36cf495b0023e8475d038535c05e4063211e1
      —
      Referenceremoved
      https://git.kernel.org/stable/c/41a117dd80371343babc52198d1114e83eb37627
      —
      Referenceremoved
      https://git.kernel.org/stable/c/4458757c020592a3094366e0fb20457383b42f92
      —
      Referenceremoved
      https://git.kernel.org/stable/c/44714dfda386884919ba366411880b6fb3c3efd3
      —
      Referenceremoved
      https://git.kernel.org/stable/c/9a397aa9b5e53ca63d4d6aefb542832eca389618
      —
      Referenceremoved
      https://git.kernel.org/stable/c/a1be1c9ece26cea69654f28b255ff9a7906b897b
      —
      Referenceremoved
      https://git.kernel.org/stable/c/ac33733b10b484d666f97688561670afd5861383
      —
      Referenceremoved
      https://git.kernel.org/stable/c/ce383ba615339f8eaec646a166d2c2b015bb5ca0
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/1fa36cf495b0023e8475d038535c05e4063211e1 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/4458757c020592a3094366e0fb20457383b42f92 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/a1be1c9ece26cea69654f28b255ff9a7906b897b Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/ac33733b10b484d666f97688561670afd5861383 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/ce383ba615339f8eaec646a166d2c2b015bb5ca0 Types: Patch
      —

      Source identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

    2. Record modifiedSiemens ADP

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/31xxx/CVE-2026-31696.json">CVE-2026-31696</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-784472.html

      Source identifier: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e

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