Use-after-free in Linux kernel - CVE-2026-64437

Vulnerability identifier: #VU139500

CSH Severity: Medium

CVSS v4: 7.1 [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]

CVE-ID: CVE-2026-64437

CWE-ID: CWE-416

Exploitation vector: Remote access

Exploit availability: No public exploit available

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.

Linux kernel
Ubuntu
linux (Ubuntu package)
linux-lowlatency (Ubuntu package)
linux-gcp (Ubuntu package)
linux-aws (Ubuntu package)
linux-ibm (Ubuntu package)
linux-oracle (Ubuntu package)
linux-realtime (Ubuntu package)
linux-fips (Ubuntu package)
linux-gkeop (Ubuntu package)
linux-gke (Ubuntu package)
linux-aws-fips (Ubuntu package)
linux-gcp-fips (Ubuntu package)

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
linux (Ubuntu package) - update to 6.8.0-147.147
linux-lowlatency (Ubuntu package) - update to 6.8.0-147.147.1
linux-gcp (Ubuntu package) - update to 6.8.0-1071.79
linux-aws (Ubuntu package) - update to 6.8.0-1067.70
linux-ibm (Ubuntu package) - update to 6.8.0-1067.68
linux-oracle (Ubuntu package) - update to 6.8.0-1064.67
linux-realtime (Ubuntu package) - update to 6.8.1-1062.63
linux-fips (Ubuntu package) - update to 6.8.0-147.147+fips1
linux-gkeop (Ubuntu package) - update to 6.8.0-1052.56
linux-gke (Ubuntu package) - update to 6.8.0-1066.74
linux-aws-fips (Ubuntu package) - update to 6.8.0-1067.70+fips1
linux-gcp-fips (Ubuntu package) - update to 6.8.0-1071.79+fips1

• 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

• Use-after-free in Linux kernel smb server
• Ubuntu update for linux, linux-aws, linux-aws-fips and more