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PatchSiren cyber security CVE debrief

CVE-2026-31666 Linux CVE debrief

A vulnerability in the Linux kernel's btrfs module could allow local attackers to corrupt extent tree data. The issue arises from an incorrect return value in the lookup_extent_data_ref() function after changing leaf nodes. This can lead to operations being performed on the wrong extent tree item. The vulnerability was resolved through a series of commits, including 4125a194db4a6cf91f619f38788272651cb97dce, 450e6a685d0cad95b15f8af152057bd0bf79f50b, ab1e022379c3c811aa72da8eb0c7507859a1d0f5, and 316fb1b3169efb081d2db910cbbfef445afa03b9. To address this vulnerability, it is crucial to review and apply patches, verify extent tree data integrity, and monitor system logs for potential corruption.

Vendor
Linux
Product
Unknown
CVSS
HIGH 7.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-04-24
Original CVE updated
2026-10-19
Advisory published
2026-04-24
Advisory updated
2026-10-19

Who should care

Linux system administrators and security teams should assess exposure and prioritize verification of affected systems, especially those with local access, to prevent potential extent tree corruption and incorrect operations. They should review and apply patches, verify extent tree data integrity, and monitor system logs for potential corruption.

Why it matters

Linux system administrators and security teams should assess exposure and prioritize verification of affected systems, especially those with local access, to prevent potential extent tree corruption and incorrect operations.

  • Potential extent tree corruption
  • Incorrect return values leading to wrong extent tree item operations
  • Local attackers could exploit this vulnerability

Technical summary

The vulnerability is caused by an incorrect return value after changing leaf nodes in the lookup_extent_data_ref() function. This issue can lead to extent tree corruption. The vulnerability was resolved through a series of commits. Linux system administrators and security teams should assess exposure and prioritize verification of affected systems, especially those with local access. The affected versions require verification from official sources. To address this vulnerability, it is crucial to review and apply patches, verify extent tree data integrity, and monitor system logs for potential corruption.

Defensive priority

Linux system administrators and security teams should assess exposure and prioritize verification of affected systems, especially those with local access, to prevent potential extent tree corruption and incorrect operations.

Recommended defensive actions

  • Review and apply the provided patches to the Linux kernel
  • Verify the integrity of extent tree data
  • Monitor system logs for potential corruption
  • Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
  • Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance
  • Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review

Evidence notes

The vulnerability is caused by an incorrect return value after changing leaf nodes in the lookup_extent_data_ref() function. This issue can lead to extent tree corruption. The affected versions require verification from official sources. Linux system administrators should verify the integrity of extent tree data and monitor system logs for potential corruption. The vulnerability was resolved through a series of commits, including 4125a194db4a6cf91f619f38788272651cb97dce, 450e6a685d0cad95b15f8af152057bd0bf79f50b, ab1e022379c3c811aa72da

Sources and references

Verified primary and authoritative sources

  • CVE-2026-31666 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-31666

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-31666 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-31666

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • btrfs: fix incorrect return value after changing leaf in lookup_extent_data_ref()

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/31xxx/CVE-2026-31666.json

    cve_program_cvelist_v5

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/4125a194db4a6cf91f619f38788272651cb97dce

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/450e6a685d0cad95b15f8af152057bd0bf79f50b

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/ab1e022379c3c811aa72da8eb0c7507859a1d0f5

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/316fb1b3169efb081d2db910cbbfef445afa03b9

    Supplemental source

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.