CVE-2026-64600
xfs: resample the data fork mapping after cycling ILOCK
- Published
- Jul 23, 2026
- Updated
- Aug 17, 2026
- Assigning CNA
- Linux
- Evidence observed
- Aug 14, 2026
Primary CVSS
nvd · CVSS 3.1
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HLow · next 30 days
- Percentile
- 39.5%
- Model date
- Sep 21, 2026
EPSS is a statistical estimate, not a certainty or a measure of impact. Combine it with CVSS, KEV status, exposure and your environment.
Summary
In the Linux kernel, the following vulnerability has been resolved: xfs: resample the data fork mapping after cycling ILOCK xfs_reflink_fill_{cow_hole,delalloc} are both presented with an inode, a data fork mapping, and a cow fork mapping. Unfortunately, these two helpers cycle the ILOCK to grab a transaction, which means that the mappings are stale as soon as we reacquire the ILOCK. Currently we refresh the cow fork mapping by re-calling xfs_find_trim_cow_extent, but we don't refresh the data fork mapping beforehand, which means that the xfs_bmap_trim_cow in that function queries the refcount btree about the wrong physical blocks and returns an inaccurate value in *shared. If *shared is now false, the directio write proceeds with a stale data fork mapping. Fix this by querying the data fork mapping if the sequence counter changes across the ILOCK cycle.
Sources
9- CVE-2026-64600Research
CVE-2026-64600
A C-based Linux security utility for detecting, safely verifying (Proof of Concept), and mitigating CVE-2026-64600 (RefluXFS). It provides kernel vulnerability assessment, XFS reflink detection, a safe race-condition PoC, and layered mitigation using SystemTap and XFS hardening.
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