CVE-2026-89766: Linux Vulnerability

Description

In the Linux kernel, the following vulnerability has been resolved: pidfd: hold exec_update_lock around namespace ioctl The PIDFD_GET_*_NAMESPACE ioctls in pidfd_ioctl() perform a filesystem credentials ptrace access check before handing out a namespace file descriptor. The accompanying comment states that the code "mirrors nsfs behavior", but, unlike the corresponding procfs paths, it does so without holding the target task's exec_update_lock. proc_ns_get_link() and proc_ns_readlink() both take exec_update_lock for reading around the ptrace check and the namespace lookup, so that the credentials used for the access decision match those of the task when its namespace is read. Without it, a caller can pass the check against the target's old credentials and then read the namespace after the target has execve()'d a setuid binary and committed new credentials -- accessing namespace information it should have been denied. Hold exec_update_lock for reading around the ptrace check and the namespace lookup so that pidfd truly mirrors nsfs behavior, as the comment already claims. open_namespace() itself runs outside the lock: once a namespace reference is obtained it carries its own refcount and is opened with the caller's own credentials, so a concurrent execve() on the target can no longer affect the outcome.

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= 5b08bd408534bfb3a7cf5778da5b27d4e4fffe12, < cf24ce48d60225fdbee68ed2058763a1fd172ff3; >= 5b08bd408534bfb3a7cf5778da5b27d4e4fffe12, < e89318aa8629969e86548b05e7c19283af3f0efb; >= 5b08bd408534bfb3a7cf5778da5b27d4e4fffe12, < 9688a46802939da28f00cb40e8129615d5d4af39
Linux	Linux	6.11

References

Timeline

Published: Sep 11, 2026
Last Modified: Sep 11, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-89766?

In the Linux kernel, the following vulnerability has been resolved: pidfd: hold exec_update_lock around namespace ioctl The PIDFD_GET_*_NAMESPACE ioctls in pidfd_ioctl() perform a filesystem credentials ptrace access check before handing out a namespace file descriptor. The accompanying comment states that the code "mirrors nsfs behavior", but, unlike the corresponding procfs paths, it does so without holding the target task's exec_update_lock. proc_ns_get_link() and proc_ns_readlink() both take exec_update_lock for reading around the ptrace check and the namespace lookup, so that the credentials used for the access decision match those of the task when its namespace is read. Without it, a caller can pass the check against the target's old credentials and then read the namespace after the target has execve()'d a setuid binary and committed new credentials -- accessing namespace information it should have been denied. Hold exec_update_lock for reading around the ptrace check and the namespace lookup so that pidfd truly mirrors nsfs behavior, as the comment already claims. open_namespace() itself runs outside the lock: once a namespace reference is obtained it carries its own refcount and is opened with the caller's own credentials, so a concurrent execve() on the target can no longer affect the outcome.

How severe is CVE-2026-89766?

Severity scoring for CVE-2026-89766 is pending analysis.

How do I fix CVE-2026-89766?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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