{"id":"CVE-2026-89766","summary":"pidfd: hold exec_update_lock around namespace ioctl","details":"In the Linux kernel, the following vulnerability has been resolved:\n\npidfd: hold exec_update_lock around namespace ioctl\n\nThe PIDFD_GET_*_NAMESPACE ioctls in pidfd_ioctl() perform a filesystem\ncredentials ptrace access check before handing out a namespace file\ndescriptor.  The accompanying comment states that the code \"mirrors nsfs\nbehavior\", but, unlike the corresponding procfs paths, it does so without\nholding the target task's exec_update_lock.\n\nproc_ns_get_link() and proc_ns_readlink() both take exec_update_lock for\nreading around the ptrace check and the namespace lookup, so that the\ncredentials used for the access decision match those of the task when its\nnamespace is read.  Without it, a caller can pass the check against the\ntarget's old credentials and then read the namespace after the target has\nexecve()'d a setuid binary and committed new credentials -- accessing\nnamespace information it should have been denied.\n\nHold exec_update_lock for reading around the ptrace check and the\nnamespace lookup so that pidfd truly mirrors nsfs behavior, as the comment\nalready claims.  open_namespace() itself runs outside the lock: once a\nnamespace reference is obtained it carries its own refcount and is opened\nwith the caller's own credentials, so a concurrent execve() on the target\ncan no longer affect the outcome.","modified":"2026-09-12T11:47:16.947088896Z","published":"2026-09-11T19:47:06.597Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89766.json","cna_assigner":"Linux"},"references":[{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9688a46802939da28f00cb40e8129615d5d4af39"},{"type":"WEB","url":"https://git.kernel.org/stable/c/cf24ce48d60225fdbee68ed2058763a1fd172ff3"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e89318aa8629969e86548b05e7c19283af3f0efb"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89766.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89766"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"5b08bd408534bfb3a7cf5778da5b27d4e4fffe12"},{"fixed":"cf24ce48d60225fdbee68ed2058763a1fd172ff3"},{"fixed":"e89318aa8629969e86548b05e7c19283af3f0efb"},{"fixed":"9688a46802939da28f00cb40e8129615d5d4af39"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89766.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.11.0"},{"fixed":"6.18.51"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.4"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89766.json"}}],"schema_version":"1.9.0"}