Off-by-one in Linux kernel - CVE-2026-80537
Published: August 27, 2026
Vulnerability identifier: #VU145960
CSH Severity: Low
CVSS v4: 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]
CVE-ID: CVE-2026-80537
CWE-ID: CWE-193
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vulnerability details
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.
Affected software
Linux kernel
How to mitigate CVE-2026-80537
Install security update from vendor's repository.
Linux kernel - update to 7.0 rc3