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🐧
🐧 Linux
Not in CISA KEV
CRITICAL severity

CVE-2026-53309 — Kernel

CRITICAL

CVE-2026-53309 is a critical-severity (CVSS 9.8) CWE-193 vulnerability in Kernel. A fix is available for Kernel — see the affected versions and patch details below.

ocfs2/dlm: fix off-by-one in dlm_match_regions() region comparison

Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.4%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs32th percentile — riskier than 32% of all scored CVEsHighest risk
0.00%0.30%0.60%0.90%0.4%0.4%0.4%0.4%0.4%Jul 26Sep 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-53309 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
🐧Kernel

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Linux packages — download data is not available via public APIs for these ecosystems.

Description

In the Linux kernel, the following vulnerability has been resolved:

ocfs2/dlm: fix off-by-one in dlm_match_regions() region comparison

The local-vs-remote region comparison loop uses '<=' instead of '<', causing it to read one entry past the valid range of qr_regions. The other loops in the same function correctly use '<'.

Fix the loop condition to use '<' for consistency and correctness.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐧LinuxKernel≥ 2.6.37&&< 5.10.2585.10.258

Affected Products

1 product · 7 configurations
OS
linux kernellinux
≥ 6.19 && < 7.0.10
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Kernel, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update Kernel to 5.10.258 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-53309 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

UbuntuCRITICAL
USN-8665-1UbuntuUSN-8566-1UbuntuUSN-8567-1UbuntuUSN-8568-1UbuntuUSN-8569-1UbuntuUSN-8574-1UbuntuUSN-8575-1UbuntuUSN-8576-1Ubuntu

Frequently Asked Questions

In the Linux kernel, the following vulnerability has been resolved: ocfs2/dlm: fix off-by-one in dlm_match_regions() region comparison The local-vs-remote region comparison loop uses '<=' instead of '<', causing it to read one entry past the valid range of qr_regions. The other loops in the same function correctly use '<'. Fix the loop condition to use '<' for consistency and correctness.
O3 Security · Impact-Aware SCA

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CVE-2026-53309: Kernel — Fixed in 5.10.258