CVE-2026-89766

Received Received - Intake

Race Condition in Linux Kernel PIDFD Namespace Handling

Publication date: 2026-09-11

Last updated on: 2026-09-11

Assigner: kernel.org

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.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-09-11

Last Modified

2026-09-11

Generated

2026-09-12

AI Q&A

2026-09-12

EPSS Evaluated

N/A

NVD

CVE-2026-89766

EUVD

EUVD-2026-76678

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability in the Linux kernel involves the PIDFD_GET_*_NAMESPACE ioctls in pidfd_ioctl(). These ioctls perform a filesystem credentials ptrace access check but fail to hold the target task's exec_update_lock during the check. This allows a caller to bypass access restrictions by checking against old credentials before the target task executes a setuid binary, then accessing the namespace after new credentials are committed.

Detection Guidance

This vulnerability is specific to the Linux kernel and requires checking the kernel version and patch status. Use 'uname -a' to check the kernel version and compare it against patched versions. No direct detection commands are provided in the context.

Impact Analysis

An attacker with access to the system could exploit this flaw to gain unauthorized access to namespace information of other processes. This could lead to information disclosure, privilege escalation, or further exploitation of the system by bypassing intended access controls.

Mitigation Strategies

Update the Linux kernel to the latest patched version. Monitor vendor advisories for kernel updates addressing this issue. No specific mitigation steps are detailed beyond patching.

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