Integer underflow in Linux kernel - CVE-2026-89640
Published: September 12, 2026
Vulnerability identifier: #VU149169
CSH Severity: Low
CVSS v4: 4.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-89640
CWE-ID: CWE-191
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a local user to corrupt the ByteCount in a file-clone request.
The vulnerability exists due to an integer underflow in cifs_remap_file_range() when issuing a clone-to-EOF operation with a source offset beyond the end of the source file. A local user can invoke a clone-to-EOF operation with an out-of-range source offset to corrupt the ByteCount in a file-clone request.
Affected software
Linux kernel
How to mitigate CVE-2026-89640
Install security update from vendor's repository.