CVE-2026-43187: In the Linux kernel, the following vulnerability has been resolved: xfs: delete attr leaf freemap entries when empty Back in commit 2a2b5932db6758 (...

Description

In the Linux kernel, the following vulnerability has been resolved: xfs: delete attr leaf freemap entries when empty Back in commit 2a2b5932db6758 ("xfs: fix attr leaf header freemap.size underflow"), Brian Foster observed that it's possible for a small freemap at the end of the end of the xattr entries array to experience a size underflow when subtracting the space consumed by an expansion of the entries array. There are only three freemap entries, which means that it is not a complete index of all free space in the leaf block. This code can leave behind a zero-length freemap entry with a nonzero base. Subsequent setxattr operations can increase the base up to the point that it overlaps with another freemap entry. This isn't in and of itself a problem because the code in _leaf_add that finds free space ignores any freemap entry with zero size. However, there's another bug in the freemap update code in _leaf_add, which is that it fails to update a freemap entry that begins midway through the xattr entry that was just appended to the array. That can result in the freemap containing two entries with the same base but different sizes (0 for the "pushed-up" entry, nonzero for the entry that's actually tracking free space). A subsequent _leaf_add can then allocate xattr namevalue entries on top of the entries array, leading to data loss. But fixing that is for later. For now, eliminate the possibility of confusion by zeroing out the base of any freemap entry that has zero size. Because the freemap is not intended to be a complete index of free space, a subsequent failure to find any free space for a new xattr will trigger block compaction, which regenerates the freemap. It looks like this bug has been in the codebase for quite a long time.

Metrics

CVSS 3.1

8.8/10

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

EPSS Probability

0.47%

37.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-191

Affected Software

Vendor	Product	Versions
Linux	Linux Kernel	>= 2.6.12.1, < 5.10.252
Linux	Linux Kernel	>= 5.11, < 5.15.202
Linux	Linux Kernel	>= 5.16, < 6.1.165
Linux	Linux Kernel	>= 6.2, < 6.6.128
Linux	Linux Kernel	>= 6.7, < 6.12.75
Linux	Linux Kernel	>= 6.13, < 6.18.16
Linux	Linux Kernel	>= 6.19, < 6.19.6
Linux	Linux Kernel	2.6.12

References

Timeline

Published: May 6, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-43187?

In the Linux kernel, the following vulnerability has been resolved: xfs: delete attr leaf freemap entries when empty Back in commit 2a2b5932db6758 ("xfs: fix attr leaf header freemap.size underflow"), Brian Foster observed that it's possible for a small freemap at the end of the end of the xattr entries array to experience a size underflow when subtracting the space consumed by an expansion of the entries array. There are only three freemap entries, which means that it is not a complete index of all free space in the leaf block. This code can leave behind a zero-length freemap entry with a nonzero base. Subsequent setxattr operations can increase the base up to the point that it overlaps with another freemap entry. This isn't in and of itself a problem because the code in _leaf_add that finds free space ignores any freemap entry with zero size. However, there's another bug in the freemap update code in _leaf_add, which is that it fails to update a freemap entry that begins midway through the xattr entry that was just appended to the array. That can result in the freemap containing two entries with the same base but different sizes (0 for the "pushed-up" entry, nonzero for the entry that's actually tracking free space). A subsequent _leaf_add can then allocate xattr namevalue entries on top of the entries array, leading to data loss. But fixing that is for later. For now, eliminate the possibility of confusion by zeroing out the base of any freemap entry that has zero size. Because the freemap is not intended to be a complete index of free space, a subsequent failure to find any free space for a new xattr will trigger block compaction, which regenerates the freemap. It looks like this bug has been in the codebase for quite a long time.

How severe is CVE-2026-43187?

CVE-2026-43187 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 0.47% probability of exploitation in the next 30 days.

How do I fix CVE-2026-43187?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.