Linux Kernel pidfd Namespace Info Leak via Missing exec_update_lock
CVE-2026-89766 Published on September 11, 2026
pidfd: hold exec_update_lock around namespace ioctl
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.
Products Associated with CVE-2026-89766
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Affected Versions
Linux:- Version 5b08bd408534bfb3a7cf5778da5b27d4e4fffe12 and below cf24ce48d60225fdbee68ed2058763a1fd172ff3 is affected.
- Version 5b08bd408534bfb3a7cf5778da5b27d4e4fffe12 and below e89318aa8629969e86548b05e7c19283af3f0efb is affected.
- Version 5b08bd408534bfb3a7cf5778da5b27d4e4fffe12 and below 9688a46802939da28f00cb40e8129615d5d4af39 is affected.
- Version 6.11 is affected.
- Before 6.11 is unaffected.
- Version 6.18.51, <= 6.18.* is unaffected.
- Version 7.2.4, <= 7.2.* is unaffected.
- Version 7.3-rc1, <= * is unaffected.