MediumCVE-2026-80521

    Linux Kernel: Race Condition (CVE-2026-80521)

    Published Last modified Sources: Debian LTS, SUSE, Ubuntu, Red Hat, Debian, BSI, CVE.org, Msrc Update Guide

    What is affected, what to do

    A flaw was found in the Linux kernel's `af_unix` component. A race condition during concurrent `send()` and `close()` operations can lead to the garbage collector (GC) partially freeing a Strongly Connected Component (SCC).

    An exploit is publicly available. Update Linux Kernel to version 6.1.189, Linux Kernel to version 6.6.158, Linux Kernel to version 6.12.111.

    Affected
    • Linux Kernel lt 6.1.141..6.1.189
    • Linux Kernel lt 6.6.93..6.6.158
    • Linux Kernel lt 6.10..6.12.111
    • Linux Kernel lt 6.13..6.18.53
    • Linux Kernel lt 6.19..7.1.10
    Fixed in
    • Linux Kernel 6.1.189
    • Linux Kernel 6.6.158
    • Linux Kernel 6.12.111
    • Linux Kernel 6.18.53
    • Linux Kernel 7.1.10
    • Linux Kernel 7.2

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

    Metrics

    4.7

    Priority

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

    Source: Vendor (CNA), CVSS v3

    4.7

    CVSS v3

    Severity Medium on the scale from 0 to 10.

    Source: Debian LTS, SUSE, Ubuntu, Red Hat, Debian, BSI, CVE.org, Msrc Update Guide

    0.2 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 7.3

    Show all metrics
    Severity
    Medium
    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
    48.60 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
    PoC (publicly reported)
    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
    4.7 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
    4.7
    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
    0.2 %
    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
    7.3
    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
    Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
    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

    A flaw was found in the Linux kernel's `af_unix` component. A race condition during concurrent `send()` and `close()` operations can lead to the garbage collector (GC) partially freeing a Strongly Connected Component (SCC). This inconsistent state may cause subsequent GC operations to iterate over a partially freed entry, potentially leading to system instability or a denial of service.

    Source: Debian LTS Advisories, suse_csaf, Ubuntu Security Notices, redhat_csaf, Debian Security Advisories, BSI WID Portal, BSI CSAF, cvelistv5, NVD (NIST), 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
    • 6.6.93 – < 6.6.158
    • 6.10 – < 6.12.111
    • 6.13 – < 6.18.53
    • 6.19 – < 7.1.10
    • 6.1.141 – < 6.1.189
    • —
    • 6.6.158
    • 6.12.111
    • 6.18.53
    • 7.1.10
    • 6.1.189
    • 7.2

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianlinuxbookworm
    Linuxdebianlinuxtrixie
    Linuxdebianlinux-6.12bookworm

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    PoC-in-GitHub (nomi-sec)Container_escape-CVE-2026-80521-CVE-2026-52910 (opens in a new tab)github.comPoC (publicly reported)reported, not verified
    PoC-in-GitHub (nomi-sec)Container_escape (opens in a new tab)github.comPoC (publicly reported)reported, not verified

    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 3 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/80xxx/CVE-2026-80521.json">CVE-2026-80521</a>
      Referenceadded
      —
      https://git.kernel.org/stable/c/2b6c2842692d08e7acaf32d1eb47f95def35f3fe
      Referenceadded
      —
      https://git.kernel.org/stable/c/6fda5c51b8e43a8440f76e65c89d9f95ddb2ef33

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

    2. Record modifiedLinux

      Show 3 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/80xxx/CVE-2026-80521.json">CVE-2026-80521</a>
      Referenceadded
      —
      https://git.kernel.org/stable/c/1293fd69a50d188a5788b08ba3741a3e86be1608
      Referenceadded
      —
      https://git.kernel.org/stable/c/fe198b077864feafd4aa4b33b1a5ce26f50195a2

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

    Linked advisories

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