SB20260727165 - Use-after-free in Linux kernel smb server
Published: July 27, 2026
Security Bulletin ID
SB20260727165
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-2026-64396)
CWE-ID: CWE-416 - Use After Free
CVSSv4: 6 [CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
The vulnerability allows a remote user to cause a denial of service.
The vulnerability exists due to use-after-free in the SMB2 lock handling logic in fs/smb/server/smb2pdu.c when canceling a deferred SMB2_LOCK request. A remote user can send crafted SMB lock and cancellation requests to cause a denial of service.
The issue is triggered by a race between deferred-lock cleanup and asynchronous cancellation while processing blocking byte-range locks.
Remediation
Install update from vendor's website.
References
- https://git.kernel.org/stable/c/367c42a611fe488b7b03f1f6737f4dee0e8b20a2
- https://git.kernel.org/stable/c/463bbd79698513af4dad50fe1c573825f297ca2e
- https://git.kernel.org/stable/c/5aa1cb01155f96824003baf7997cdf1f150caba3
- https://git.kernel.org/stable/c/5c75275c0fc9a2deb0d8f5604edcb16f288171c8
- https://git.kernel.org/stable/c/7703fd9aba1f2483c8e55f9ff73b7663e0761ed9
- https://git.kernel.org/stable/c/d20d1c8ba5765d1d12eefc0aee6385ab3f240e1e