Time-of-check Time-of-use (TOCTOU) Race Condition in Linux kernel - CVE-2026-89766
Published: September 12, 2026
Vulnerability identifier: #VU149040
CSH Severity: Low
CVSS v4: 2 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-89766
CWE-ID: CWE-367
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a local user to disclose namespace information.
The vulnerability exists due to a time-of-check time-of-use race condition in pidfd_ioctl() when performing PIDFD_GET_*_NAMESPACE ioctls while a target task executes a setuid binary. A local user can race a namespace ioctl with the target task's execve operation to disclose namespace information.
Affected software
Linux kernel
How to mitigate CVE-2026-89766
Install security update from vendor's repository.