# CVE-2026-64600

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.

- Page: https://www.vulneraibility.com/cve/CVE-2026-64600
- CVSS: 7.8
- Known exploited: not in CISA KEV as of our last sync
- EPSS: 0.47% (percentile 40.9)
- Unvetted proof-of-concept code on GitHub: 10 GitHub proofs of concept (first 2026-07-22)
- CISA SSVC: exploitation none, automatable no, technical impact total (assessed 2026-10-16)
- Weakness: CWE-362
- Published: 2026-07-23

## Affected versions

- Linux: affected >= 3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 and < dc11be133efca5fe3a2fb02b016dee825cc12f18; >= 3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 and < b8c9aa832b52680ee40d6cab0efb081f9a69df05; >= 3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 and < 50f0012da1040f69a4e788cd9aed587c9a04983f; >= 3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 and < e705d81a7193dd19e69b8e2bad4696d78a4ea075; >= 3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 and < 206c09b04dc5469c7ff14d8aceff2d47c88078d9; >= 3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 and < 44f891bc088958399eec27f7604928694aa35581; >= 3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 and < 2f4acd0fcd862e22eab45690ec2c08c80b6ef2e7; 4.11; fixed in < 4.11, >= 5.15.212 and <= 5.15.*, >= 6.1.178 and <= 6.1.*, >= 6.6.145 and <= 6.6.*, >= 6.12.96 and <= 6.12.*, >= 6.18.39 and <= 6.18.*, >= 7.1.4 and <= 7.1.*, >= 7.2 and <= *

A version outside these ranges is not a statement that it is unaffected.

## References

- [other] https://git.kernel.org/stable/c/dc11be133efca5fe3a2fb02b016dee825cc12f18
- [other] https://git.kernel.org/stable/c/b8c9aa832b52680ee40d6cab0efb081f9a69df05
- [other] https://git.kernel.org/stable/c/50f0012da1040f69a4e788cd9aed587c9a04983f
- [other] https://git.kernel.org/stable/c/e705d81a7193dd19e69b8e2bad4696d78a4ea075
- [other] https://git.kernel.org/stable/c/206c09b04dc5469c7ff14d8aceff2d47c88078d9
- [other] https://git.kernel.org/stable/c/44f891bc088958399eec27f7604928694aa35581
- [other] https://git.kernel.org/stable/c/2f4acd0fcd862e22eab45690ec2c08c80b6ef2e7
- [other] https://cdn2.qualys.com/advisory/2026/07/22/RefluXFS.txt
- [other] http://www.openwall.com/lists/oss-security/2026/07/22/14
- [other] http://www.openwall.com/lists/oss-security/2026/07/22/18
- [other] http://www.openwall.com/lists/oss-security/2026/07/22/19
- [other] http://www.openwall.com/lists/oss-security/2026/07/31/3
- [other] http://www.openwall.com/lists/oss-security/2026/08/03/4
- [other] http://www.openwall.com/lists/oss-security/2026/08/03/8

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Summary, impact and action are written by the vulneraibility.com AI analysis pipeline from the CVE record, NVD, CISA and FIRST data; verify against the references.