{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-98260", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-25T10:25:14.332Z", "datePublished": "2026-10-06T08:45:24.711Z", "dateUpdated": "2026-10-19T09:16:31.364Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T09:16:31.364Z" }, "descriptions": [ { "lang": "en", "value": "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() ]" } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The bug needs local syscalls: timer_create(CLOCK_THREAD_CPUTIME_ID) and timer_settime() on a non-leader thread, then execve(). That thread's exec must fail after de_thread() in begin_new_exec() (e.g. exec_mmap() returning -EINTR on SIGKILL). No remote protocol carries any of this input.\nAC:L - The attacker controls both sides of the race. Their own parent sends SIGKILL while exec_mmap() waits on down_write_killable(exec_update_lock) or mmap_read_lock_killable(old_mm), and they can create that lock contention with their own CLONE_VM or /proc readers. No condition outside their control is needed.\nPR:L - Arming a thread CPU timer, calling execve and signalling one's own child are all available to any unprivileged user, with no capability checks on this path. A local unprivileged account is enough.\nUI:N - The attacker's own processes perform every step (timer arm, execve from a non-leader thread, SIGKILL, wait4 reap), so no victim action is needed.\nS:U - The memory corruption is inside the kernel that the attacker's process runs on. The outcome is a normal local privilege escalation, with no VM or sandbox boundary crossed.\nC:H - exit_itimers() frees the k_itimer while its cpu_timer node is still linked in the task's posix_cputimers rbtree. The freed slab object can be reclaimed with attacker-sprayed data, giving a use-after-free that can be turned into kernel memory disclosure.\nI:H - When release_task() reaps the task, posix_cpu_timers_exit() -> cleanup_timerqueue() -> timerqueue_del() calls rb_erase on the freed node and rewrites rbtree pointers in reclaimed memory. That is a use-after-free write which can be used for privilege escalation.\nA:H - The rbtree erase on freed memory corrupts kernel data and can oops or panic the kernel. Any unprivileged user can repeat it at will." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/exec.c" ], "versions": [ { "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59", "lessThan": "6f1977cea3e85cd8ab55fb337d3e1725fe61d1ce", "status": "affected", "versionType": "git" }, { "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59", "lessThan": "d9ae467e617ca29b825493a362bf0d75ad5f4ac3", "status": "affected", "versionType": "git" }, { "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59", "lessThan": "75aa08b93c65766040f9ca99f41ac85ad22596b6", "status": "affected", "versionType": "git" }, { "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59", "lessThan": "d602877baf36c43c788a5f472c977e0be414029f", "status": "affected", "versionType": "git" }, { "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59", "lessThan": "acb03d3881818581052924a9bbbe92b8741ed448", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/exec.c" ], "versions": [ { "version": "5.7", "status": "affected" }, { "version": "0", "lessThan": "5.7", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.158", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.112", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.54", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.8", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.7", "versionEndExcluding": "6.6.158" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.7", "versionEndExcluding": "6.12.112" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.7", "versionEndExcluding": "6.18.54" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.7", "versionEndExcluding": "7.2.8" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.7", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/6f1977cea3e85cd8ab55fb337d3e1725fe61d1ce" }, { "url": "https://git.kernel.org/stable/c/d9ae467e617ca29b825493a362bf0d75ad5f4ac3" }, { "url": "https://git.kernel.org/stable/c/75aa08b93c65766040f9ca99f41ac85ad22596b6" }, { "url": "https://git.kernel.org/stable/c/d602877baf36c43c788a5f472c977e0be414029f" }, { "url": "https://git.kernel.org/stable/c/acb03d3881818581052924a9bbbe92b8741ed448" } ], "title": "exec: Cleanup POSIX timers right after de_thread()", "x_generator": { "engine": "bippy-1.2.0" } } } }