CVE-2026-64600
Published: July 23, 2026Last modified: August 10, 2026
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.
Severity score breakdown
| Parameter | Value |
|---|---|
| Base score | 7.8 |
| Attack Vector | LOCAL |
| Attack complexity | LOW |
| Privileges required | LOW |
| User interaction | NONE |
| Scope | UNCHANGED |
| Confidentiality | HIGH |
| Integrity impact | HIGH |
| Availability impact | HIGH |
| Vector | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
Status
| Product | Release | Package | Status |
|---|---|---|---|
| Alpaquita Linux | 23 LTS | linux-lts | Vulnerable (6.1.177-r0) |
| 25 LTS | linux-lts | Vulnerable (6.12.95-r0) | |
| Stream | linux-lts | Fixed (6.18.43-r0) |
References
- http://www.openwall.com/lists/oss-security/2026/07/22/14
- http://www.openwall.com/lists/oss-security/2026/07/22/18
- http://www.openwall.com/lists/oss-security/2026/07/22/19
- http://www.openwall.com/lists/oss-security/2026/07/31/3
- http://www.openwall.com/lists/oss-security/2026/08/03/4
- http://www.openwall.com/lists/oss-security/2026/08/03/8
- https://cdn2.qualys.com/advisory/2026/07/22/RefluXFS.txt
- https://git.kernel.org/stable/c/206c09b04dc5469c7ff14d8aceff2d47c88078d9
- https://git.kernel.org/stable/c/2f4acd0fcd862e22eab45690ec2c08c80b6ef2e7
- https://git.kernel.org/stable/c/44f891bc088958399eec27f7604928694aa35581
- https://git.kernel.org/stable/c/50f0012da1040f69a4e788cd9aed587c9a04983f
- https://git.kernel.org/stable/c/b8c9aa832b52680ee40d6cab0efb081f9a69df05
- https://git.kernel.org/stable/c/dc11be133efca5fe3a2fb02b016dee825cc12f18
- https://git.kernel.org/stable/c/e705d81a7193dd19e69b8e2bad4696d78a4ea075