SB20260912154 - Integer underflow in Linux kernel smb client
Published: September 12, 2026
Security Bulletin ID
SB20260912154
CSH Severity
Medium
Patch available
YES
Number of vulnerabilities
1
Exploitation vector
Remote access
Highest impact
Information disclosure
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 1 vulnerability.
1) Integer underflow (CVE-ID: CVE-2026-89630)
CWE-ID: CWE-191 - Integer underflow
CVSSv4: 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]
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.
Remediation
Install update from vendor's website.