Time-of-check Time-of-use (TOCTOU) Race Condition in Linux kernel - CVE-2026-64425

Vulnerability identifier: #VU139520

CSH Severity: Low

CVSS v4: 5.7 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-64425

CWE-ID: CWE-367

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to cause a denial of service.

The vulnerability exists due to improper state management in io_worker_handle_work() in io_uring/io-wq.c when processing linked work items during io_uring worker exit handling. A local user can submit linked work and trigger ring closure to cause a denial of service.

Exploitation requires a race condition where worker exit begins after the first linked item has started but before the remaining linked items are processed.

Linux kernel
Ubuntu
linux (Ubuntu package)
linux-azure (Ubuntu package)
linux-gcp-7.0 (Ubuntu package)
linux-oracle-7.0 (Ubuntu package)
linux-oem-7.0 (Ubuntu package)
linux-azure-7.0 (Ubuntu package)

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
linux (Ubuntu package) - addressed in versions 7.0.0-31.31, 7.0.0-31.31.1, 7.0.0-31.31~24.04.1, 7.0.0-1006.7, 7.0.0-1011.11~24.04.1, 7.0.0-1012.12, 7.0.0-1012.12~24.04.1
linux-azure (Ubuntu package) - addressed in versions 7.0.0-1011.11, 7.0.0-1014.14
linux-gcp-7.0 (Ubuntu package) - update to 7.0.0-1011.11~24.04.1
linux-oracle-7.0 (Ubuntu package) - update to 7.0.0-1011.11~24.04.1
linux-oem-7.0 (Ubuntu package) - update to 7.0.0-1013.13
linux-azure-7.0 (Ubuntu package) - update to 7.0.0-1014.14~24.04.1

• https://git.kernel.org/stable/c/14b7ecad2ec56699325180a744f4b19f046401bb
• https://git.kernel.org/stable/c/1636d85dc139b07c0449308f2bb5e0c7a2e0da99
• https://git.kernel.org/stable/c/29bef9934b2521f787bb15dd1985d4c0d12ae02a
• https://git.kernel.org/stable/c/6e2f51f3e06773c2ee98ad09738f0908b48f76f9
• https://git.kernel.org/stable/c/ab85765cbe3258b43dc6729af0e6ce3a87a133d8
• https://git.kernel.org/stable/c/b6f179a653a934736c88d820fe0098c3c2532549
• https://git.kernel.org/stable/c/d179533c610e1b4c6aa436e3c1fd1b719d2c727c
• https://git.kernel.org/stable/c/ea61b04e1d7242cb37f5ed2cc91cf21a493f6597

• Time-of-check Time-of-use (TOCTOU) Race Condition in Linux kernel io_uring
• Ubuntu update for linux-oem-7.0
• Ubuntu update for linux
• Ubuntu update for linux-gcp-7.0
• Ubuntu update for linux-oracle-7.0
• Ubuntu update for linux-azure
• Ubuntu update for linux-azure-7.0