{"id":"CVE-2026-53341","summary":"fhandle: fix UAF due to unlocked -\u003emnt_ns read in may_decode_fh()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nfhandle: fix UAF due to unlocked -\u003emnt_ns read in may_decode_fh()\n\nmay_decode_fh() accesses mount::mnt_ns without holding any locks; that\nmeans the mount can concurrently be unmounted, and the mnt_namespace can\nconcurrently be freed after an RCU grace period.\n\nThis race can happens as follows, assuming that the mount point was\ncreated by open_tree(..., OPEN_TREE_CLONE):\n\nthread 1            thread 2            RCU\n                    __do_sys_open_by_handle_at\n                      do_handle_open\n                        handle_to_path\n                          may_decode_fh\n                            is_mounted\n                              [mount::mnt_ns access]\n                            [mount::mnt_ns access]\n__do_sys_close\n  fput_close_sync\n    __fput\n      dissolve_on_fput\n        umount_tree\n        class_namespace_excl_destructor\n          namespace_unlock\n            free_mnt_ns\n              mnt_ns_tree_remove\n                call_rcu(mnt_ns_release_rcu)\n                                        mnt_ns_release_rcu\n                                          mnt_ns_release\n                                            kfree\n                            [mnt_namespace::user_ns access] **UAF**\n\nFix it by taking rcu_read_lock() around the mount::mnt_ns access, like\nin __prepend_path().\nAdditionally, document the semantics of mount::mnt_ns, and use WRITE_ONCE()\nfor writers that can race with lockless readers.\n\nThis bug is unreachable unless one of the following is set:\n\n - CONFIG_PREEMPTION\n - CONFIG_RCU_STRICT_GRACE_PERIOD\n\nbecause it requires an RCU grace period to happen during a syscall without\nan explicit preemption.\n\nThis doesn't seem to have interesting security impact; worst-case, it could\nleak the result of an integer comparison to userspace (from the level\ncheck in cap_capable()), cause an endless loop, or crash the kernel by\ndereferencing an invalid address.","modified":"2026-07-25T03:32:11.959498870Z","published":"2026-07-01T13:32:22.873Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/53xxx/CVE-2026-53341.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/15ea8dc42a02259d49dee38a658d40f60fcd75ed"},{"type":"WEB","url":"https://git.kernel.org/stable/c/32138633e51e6db59e474765cf93268c92b42888"},{"type":"WEB","url":"https://git.kernel.org/stable/c/40ab6644b99685755f740b872c00ef40d9aa870e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a8ed2c29fcfdac78db96c9da4e659c8a513f2a94"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/53xxx/CVE-2026-53341.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-53341"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"620c266f394932e5decc4b34683a75dfc59dc2f4"},{"fixed":"15ea8dc42a02259d49dee38a658d40f60fcd75ed"},{"fixed":"32138633e51e6db59e474765cf93268c92b42888"},{"fixed":"a8ed2c29fcfdac78db96c9da4e659c8a513f2a94"},{"fixed":"40ab6644b99685755f740b872c00ef40d9aa870e"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-53341.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.11.0"},{"fixed":"6.12.95"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.36"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.0.13"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-53341.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}