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Linux KernelOperating system · Linux

CVE-2026-53309

CRITICAL · 9.8 CVSS v3.1 Published 2026-06-26
Fix available
A fix is available. Upgrade to 5.10.258 / 5.15.209 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Off-by-one error in Linux kernel's OCFS2 distributed lock manager (dlm_match_regions function). The local-vs-remote region comparison loop incorrectly uses '<=' instead of '<', causing an out-of-bounds read one element past the valid qr_regions array. This is a memory safety vulnerability that could lead to information disclosure or potentially be chained for code execution.

MitigationApply the kernel patch (change loop condition from '<=' to '<') or upgrade to a patched kernel version. No user-level configuration workaround exists for in-kernel bugs; this requires a kernel update.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 2.6.37, < 5.10.258>= 5.11, < 5.15.209>= 5.16, < 6.1.175>= 6.2, < 6.6.141>= 6.7, < 6.12.91>= 6.13, < 6.18.33>= 6.19, < 7.0.10

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check kernel version
    Run 'uname -r' to get the running kernel version and compare it against the affected ranges: < 5.10.258, >= 5.11 and < 5.15.209, >= 5.16 and < 6.1.175, >= 6.2 and < 6.6.141, >= 6.7 and < 6.12.91, >= 6.13 and < 6.18.33, >= 6.19 and < 7.0.10
    Affected if Kernel version falls within any of the affected ranges listed in the CVE
  2. Check if OCFS2 filesystem is mounted
    Run 'mount | grep -i ocfs2' to see if any OCFS2 filesystems are currently mounted
    Affected if OCFS2 filesystems are mounted and the kernel version is in the affected range
  3. Check if OCFS2 dlm module is loaded
    Run 'lsmod | grep -i dlm' or check /proc/modules to see if the distributed lock manager module is loaded
    Affected if The dlm module is loaded and the kernel version is in the affected range

System is vulnerable if the running kernel version falls within the affected version ranges AND OCFS2/dlm is in use on the system

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 5.10.258 / 5.15.209 / 6.1.175 or later
Fixed in 5.10.2585.15.2096.1.175
Vendor patch git.kernel.org →
Interim mitigation

Apply the kernel patch (change loop condition from '<=' to '<') or upgrade to a patched kernel version. No user-level configuration workaround exists for in-kernel bugs; this requires a kernel update.

Recommended fix High confidence

5.10.258 (or 5.15.209, 6.1.175, or 6.6.141 depending on your branch - choose the next stable release in your version line)

  1. Identify the currently running Linux kernel version using `uname -r`
  2. Based on your current kernel version, upgrade to one of the following fixed releases that includes the patch: 5.10.258 or newer, 5.15.209 or newer, 6.1.175 or newer, or 6.6.141 or newer
  3. For Debian/Ubuntu: Run `apt update && apt upgrade` or install specific kernel package
  4. For RHEL/CentOS: Run `yum update kernel`
  5. For Fedora: Run `dnf update kernel`
  6. Reboot the system to load the new kernel
  7. Verify the new kernel version is running using `uname -r` and confirm it meets or exceeds the minimum fixed version for your branch
Caveat Kernel upgrades may require rebooting and could have compatibility issues with custom drivers or modules; test in staging first

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-53309 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data