PatchSiren

PatchSiren cyber security CVE debrief

CVE-2026-89836 Linux CVE debrief

A race condition vulnerability in the Linux kernel's f2fs file system can lead to livelock and bad page state issues. The vulnerability is caused by a faulty folio_nr_pages() function that can be triggered when invalidating a large folio from the page cache. This issue arises when f2fs_get_read_data_folio() calls f2fs_folio_put() before folio_nr_pages(), leaving a window where a concurrent truncate or folio split can shrink the compound folio or free it before the invalidate range is computed. An undersized range then leaves split sub-folios in mapping->i_pages, which can later interact badly with truncate and reclaim. Linux kernel developers and maintainers should review and apply

Vendor
Linux
Product
Unknown
CVSS
HIGH 7.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-09-16
Original CVE updated
2026-10-19
Advisory published
2026-09-16
Advisory updated
2026-10-19

Who should care

Linux kernel developers and maintainers, Linux distribution maintainers, and users of Linux-based systems should be aware of this vulnerability and take necessary actions to patch vulnerable Linux kernel versions to prevent potential issues. System administrators should monitor system logs for signs of livelock and bad page state issues.

Why it matters

A race condition vulnerability in the Linux kernel's f2fs file system can lead to livelock and bad page state issues. Defenders should prioritize patching vulnerable Linux kernel versions to prevent potential issues.

  • Defenders should prioritize patching vulnerable Linux kernel versions to prevent potential livelock and bad page state issues
  • System administrators should monitor system logs for signs of livelock and bad page state issues
  • Linux kernel developers and maintainers should review and apply the patches provided by the Linux kernel maintainers

Technical summary

The vulnerability is caused by a faulty folio_nr_pages() function that can be triggered when invalidating a large folio from the page cache. This can lead to livelock and bad page state issues. The issue arises when f2fs_get_read_data_folio() calls f2fs_folio_put() before folio_nr_pages(), leaving a window where a concurrent truncate or folio split can shrink the compound folio or free it before the invalidate range is computed. Linux kernel developers and maintainers should review and apply patches provided by the Linux kernel maintainers to fix this issue.

Defensive priority

High

Recommended defensive actions

  • Review and apply the patches provided by the Linux kernel maintainers
  • Update to the latest Linux kernel version that includes the fix
  • Monitor system logs for signs of livelock and bad page state issues
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review.
  • Track exceptions, retest remediated assets,
  • Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.
  • Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed.

Evidence notes

The vulnerability is related to the f2fs file system in the Linux kernel. The issue arises when f2fs_get_read_data_folio() calls f2fs_folio_put() before folio_nr_pages() when invalidating a large folio from the page cache.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-89836 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-89836

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

  • CVE-2026-89836 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-89836

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

Supplemental references

  • f2fs: fix folio_nr_pages() race after put in large folio invalidate

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/89xxx/CVE-2026-89836.json

    cve_program_cvelist_v5

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/cc34df18da92f68f9b384c3ae95ad64be46cb5ee

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/0dab71381f1b4d12dc2056f8bd5aaa9d93ce9082

    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.