Out-of-bounds write in Linux kernel - CVE-2026-89493
Published: September 12, 2026
Vulnerability identifier: #VU149308
CSH Severity: Low
CVSS v4: 4.6 [CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-89493
CWE-ID: CWE-787
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a local privileged user to perform out-of-bounds memory reads and writes.
The vulnerability exists due to improper validation of refcount record bounds in ocfs2_validate_refcount_block() when processing crafted refcount blocks during reflink operations. A local privileged user can mount a crafted or corrupted ocfs2 image and issue a reflink operation to perform out-of-bounds memory reads and writes.
A raw write to the block device backing an already-mounted ocfs2 filesystem can also introduce a malicious refcount block.
Affected software
Linux kernel
How to mitigate CVE-2026-89493
Install security update from vendor's repository.