{"id":"CVE-2026-98260","summary":"exec: Cleanup POSIX timers right after de_thread()","details":"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-\u003eit.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-\u003epoint_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() ]","modified":"2026-10-08T02:52:55.327808398Z","published":"2026-10-06T08:45:24.711Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98260.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/6f1977cea3e85cd8ab55fb337d3e1725fe61d1ce"},{"type":"WEB","url":"https://git.kernel.org/stable/c/75aa08b93c65766040f9ca99f41ac85ad22596b6"},{"type":"WEB","url":"https://git.kernel.org/stable/c/acb03d3881818581052924a9bbbe92b8741ed448"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d602877baf36c43c788a5f472c977e0be414029f"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d9ae467e617ca29b825493a362bf0d75ad5f4ac3"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98260.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98260"},{"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":"55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59"},{"fixed":"6f1977cea3e85cd8ab55fb337d3e1725fe61d1ce"},{"fixed":"d9ae467e617ca29b825493a362bf0d75ad5f4ac3"},{"fixed":"75aa08b93c65766040f9ca99f41ac85ad22596b6"},{"fixed":"d602877baf36c43c788a5f472c977e0be414029f"},{"fixed":"acb03d3881818581052924a9bbbe92b8741ed448"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98260.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.7.0"},{"fixed":"6.6.158"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.112"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.54"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.8"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98260.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}