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Vulnerability record · CVE-2026-64600 · published 23 July 2026

CVE-2026-64600: Linux kernel race condition vulnerability

Linux · Linux Kernel

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.

7.8 CVSS 3.1 High EPSS 0.16% · top 95.8% CWE-362 · Race condition
7.8CVSS 3.1 base score
0.16%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
14References, 2 tagged exploit
18 Aug 2026Last modified by NVD

Description

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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

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

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Source: NIST National Vulnerability Database (record CVE-2026-64600), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.