SB20260727180 - Use-after-free in Linux kernel smb server
Published: July 27, 2026
Security Bulletin ID
SB20260727180
CSH Severity
Medium
Patch available
YES
Number of vulnerabilities
1
Exploitation vector
Remote access
Highest impact
Denial of service
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 1 vulnerability.
1) Use-after-free (CVE-ID: CVE-2026-64390)
CWE-ID: CWE-416 - Use After Free
CVSSv4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to a use-after-free in ksmbd byte-range lock handling when processing smb2 lock requests in smb3 multichannel environments. A remote attacker can trigger concurrent lock traversal and removal to cause a denial of service.
The issue occurs because a lock list entry can be removed under a different spinlock than the one protecting the list it belongs to.
Remediation
Install update from vendor's website.
References
- https://git.kernel.org/stable/c/22d38cf75b556c20b039743bdf3654d535b858be
- https://git.kernel.org/stable/c/427faaa52b0b399940c1a88065a5c310d10dad15
- https://git.kernel.org/stable/c/5fecc15a30cb9ebd310f7b52c1ab607edcea78f6
- https://git.kernel.org/stable/c/66eb3643164e5e1029907793926c132f8b5c6148
- https://git.kernel.org/stable/c/c1016dd1d8b2bcd1158bbaabe94a31bb7e7431fb
- https://git.kernel.org/stable/c/ea5c9bf99f626a15cc59f645dc895f2b3f01992e
- https://git.kernel.org/stable/c/fe20d492a69a6f79e637f438072b212e21ed3b78