Use-after-free in Linux kernel - CVE-2026-89641

Vulnerability identifier: #VU149170

CSH Severity: Low

CVSS v4: 0 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-89641

CWE-ID: CWE-416

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to trigger a use-after-free.

The vulnerability exists due to use-after-free in the CIFS client's cifs_file_set_size() function when falling back to path-based file-size operations after a failed handle-based set_file_size() RPC. A local user can cause the fallback to reuse a freed tcon to trigger a use-after-free.

Exploitation requires a tlink to be removed during reconnection or session teardown and its last reference to be released.

Linux kernel
Ubuntu
linux (Ubuntu package)
linux-aws (Ubuntu package)
linux-gcp (Ubuntu package)
linux-oracle (Ubuntu package)
linux-ibm (Ubuntu package)
linux-hwe-7.0 (Ubuntu package)
linux-oem-7.0 (Ubuntu package)

Install security update from vendor's repository.

linux (Ubuntu package) - update to 7.0.0-42.42
linux-aws (Ubuntu package) - update to 7.0.0-1016.17
linux-gcp (Ubuntu package) - update to 7.0.0-1016.18
linux-oracle (Ubuntu package) - update to 7.0.0-1015.16
linux-ibm (Ubuntu package) - update to 7.0.0-1017.17
linux-hwe-7.0 (Ubuntu package) - update to 7.0.0-42.42~24.04.1
linux-oem-7.0 (Ubuntu package) - update to 7.0.0-1017.17

• https://git.kernel.org/stable/c/4bea15d9c7683218f57b8c1f5f0aa75cab76af8d
• https://git.kernel.org/stable/c/4f18c9e7ee464aaae5cd9fccdb943b3fcb4655d4
• https://git.kernel.org/stable/c/b96db32fed8dfb2478d7c208f89bf383beed1535

• Use-after-free in Linux kernel smb client
• Ubuntu update for linux-oem-7.0
• Ubuntu update for linux, linux-aws, linux-gcp and more