SB20260727125 - Use-after-free in Linux kernel smb server
Published: July 27, 2026
Security Bulletin ID
SB20260727125
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-2026-64437)
CWE-ID: CWE-416 - Use After Free
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote user to cause a denial of service.
The vulnerability exists due to use-after-free in smb2_cancel() and deferred byte-range lock handling in ksmbd when processing an SMB2_CLOSE followed by an SMB2_CANCEL for the same AsyncId. A remote user can send crafted SMB requests to cause a denial of service.
Exploitation requires authentication to the SMB service and access to a locking handle associated with deferred work.
Remediation
Install update from vendor's website.
References
- https://git.kernel.org/stable/c/10f293a07f9e10e988b0ae44e2e99c631f5a68e0
- https://git.kernel.org/stable/c/12c36c99655f325befe50c26842f7deca414c381
- https://git.kernel.org/stable/c/94083db751930b1540ddff2b54d4677549c57f81
- https://git.kernel.org/stable/c/a796ba4e61d5e14e07b79a359faac69f8f9b22a3
- https://git.kernel.org/stable/c/b8e274e69ab09222c7a552c7c0c1eef9ce627fc1
- https://git.kernel.org/stable/c/ddb9239828336b36d8a3ef5943fdffb2f55b6508