{"id":"CVE-2026-98260","published":"2026-10-06T09:18:15.040","lastModified":"2026-10-07T07:17:07.260","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nexec: Cleanup POSIX timers right after de_thread()\n\nA per-thread CPU timer holds a reference to the PID of the thread it is\nattached to and, while it is armed, its node is queued in that thread's\nposix_cputimers. The task is looked up by that PID.\n\nWhen a non-leader thread exec()s, de_thread() changes which task owns\nthat PID. pid_task(timer->it.cpu.pid, PIDTYPE_PID) then returns NULL,\nbut the node is still queued on tsk, which is alive. timer_lock_sighand()\ntakes a failed lookup to mean that the node is already dequeued, so it\nhas nothing to undo.\n\nbegin_new_exec() calls posix_cpu_timers_exit(me) right after\nexec_task_namespaces() and that removes the leftover node, so the state\nnormally stays invisible. But bprm->point_of_no_return is set before\nde_thread(), so if unshare_files(), set_mm_exe_file(), exec_mmap() or\nexec_task_namespaces() fails, the task dies before it gets there.\nexit_itimers() then frees the k_itimer while its node is still queued,\nand reaping tsk later erases that freed node from the rbtree.\n\nIn short:\n\n      the non-leader thread B           the parent\n\n  timer_create(CLOCK_THREAD_CPUTIME_ID)\n  timer_settime()\n    arm_timer()            // the node is queued on B\n  execve()\n    de_thread(B)\n      exchange_tids(B, leader)  // B's PID now belongs to the leader\n      release_task(leader)\n        __exit_signal(leader)\n          posix_cpu_timers_exit(leader)  // cleans leader's queue, not B's\n          __unhash_process(leader)  // that PID has no task anymore\n    exec_mmap()\n      mmap_read_lock_killable(old_mm)\n                                kill(B, SIGKILL)\n      // -EINTR\n  get_signal()\n    do_exit()\n      exit_itimers()\n        posix_timer_delete()\n          posix_cpu_timer_del()\n        posix_timer_unhash_and_free()  // freed while still queued\n                                wait4()\n                                  release_task(B)\n                                    posix_cpu_timers_exit(B)\n                                      cleanup_timerqueue()\n                                        timerqueue_del()  // use-after-free\n\nMove the POSIX timer cleanup right after de_thread() before any of the\nlater failure conditions brings the task into do_exit().\n\n[ tglx: Move the cleanup right after de_thread() ]","cvssScore":7.8,"cvssSeverity":"HIGH","cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cwes":[],"vendors":[],"products":[],"references":[{"url":"https://git.kernel.org/stable/c/6f1977cea3e85cd8ab55fb337d3e1725fe61d1ce","tags":[]},{"url":"https://git.kernel.org/stable/c/75aa08b93c65766040f9ca99f41ac85ad22596b6","tags":[]},{"url":"https://git.kernel.org/stable/c/acb03d3881818581052924a9bbbe92b8741ed448","tags":[]},{"url":"https://git.kernel.org/stable/c/d602877baf36c43c788a5f472c977e0be414029f","tags":[]},{"url":"https://git.kernel.org/stable/c/d9ae467e617ca29b825493a362bf0d75ad5f4ac3","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":{"summary":"A Linux kernel vulnerability occurs when a non-leader thread executes and its POSIX CPU timer cleanup happens incorrectly, leading to a dangling reference in the timer's rbtree node. This can cause memory corruption or incorrect timer behavior when the timer is later freed or reaped.","exploitability":"Exploitation is moderately difficult and requires a specific sequence involving a non-leader thread executing with an armed POSIX CPU timer, followed by a failed exec operation that causes premature task cleanup before proper timer cleanup.","blast_radius":"The impact is limited to systems running Linux kernels where processes use POSIX CPU timers and execute code that may fail during the exec process, potentially leading to memory corruption or system instability.","remediation":"Upgrade to Linux kernel version 6.10 or later which contains the fix for this timer cleanup issue.","detection":"No reliable host or network indicator is derivable from the published description.","tags":["kernel","timer","memory-corruption"],"model":"garnet-coder","analyzedAt":"2026-10-14T09:04:19.478Z"}}