SB20260827106 - Off-by-one in Linux kernel xfs libxfs

Description

This security bulletin contains information about 1 vulnerability.

1) Off-by-one (CVE-ID: CVE-2026-80537)

CWE-ID: CWE-193 - Off-by-one Error

CVSSv4: 8.5 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

The vulnerability allows a local user to execute arbitrary code or cause a denial of service.

The vulnerability exists due to a slab-out-of-bounds write caused by an off-by-one error in xfs rtrefcount btree root level validation in xfs_rtrefcountbt_verify() and xfs_iformat_rtrefcount() when mounting a crafted XFS filesystem image or querying filesystem mapping information on the realtime device. A local user can mount a crafted filesystem image to execute arbitrary code or cause a denial of service.

The issue is triggered when the rtrefcount root level equals the maximum allowed level, which causes bc_nlevels to exceed bc_maxlevels by one during cursor initialization.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/8a0ecae2ecda9f9a83a496ed05c42c4b1f5c3f2d
• https://git.kernel.org/stable/c/cc3144da377de5fb422d44a2311f978623f7c900
• https://git.kernel.org/stable/c/ccebfc309441e0b37b2e6ece90f18810a489d326