Integer underflow in Linux kernel - CVE-2026-89630
Published: September 12, 2026
Vulnerability identifier: #VU149176
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-89630
CWE-ID: CWE-191
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause an out-of-bounds read.
The vulnerability exists due to an integer underflow in is_valid_oplock_break() in the SMB client when processing a specially crafted SMB oplock break message. A remote attacker can send a specially crafted SMB oplock break message to cause an out-of-bounds read.
Affected software
Linux kernel
How to mitigate CVE-2026-89630
Install security update from vendor's repository.