222 lines
14 KiB
JSON
222 lines
14 KiB
JSON
{
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"dataType": "CVE_RECORD",
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"dataVersion": "5.2",
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"cveMetadata": {
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"cveId": "CVE-2026-98260",
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"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"state": "PUBLISHED",
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"assignerShortName": "Linux",
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"dateReserved": "2026-09-25T10:25:14.332Z",
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"datePublished": "2026-10-06T08:45:24.711Z",
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"dateUpdated": "2026-10-30T12:37:58.294Z"
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},
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"containers": {
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"cna": {
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"providerMetadata": {
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"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"shortName": "Linux",
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"dateUpdated": "2026-10-30T12:37:58.294Z"
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},
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"descriptions": [
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{
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"lang": "en",
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"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() ]"
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}
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],
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"metrics": [
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{
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"cvssV3_1": {
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"version": "3.1",
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"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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"baseScore": 7.8,
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"baseSeverity": "HIGH"
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},
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"scenarios": [
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{
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"lang": "en",
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"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."
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}
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]
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}
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],
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"affected": [
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "unaffected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"fs/exec.c"
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"fs/exec.c"
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"status": "affected"
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},
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"version": "0",
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"lessThan": "5.7",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.1.191",
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"lessThanOrEqual": "6.1.*",
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"status": "unaffected",
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},
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"version": "6.6.158",
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"lessThanOrEqual": "6.6.*",
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"status": "unaffected",
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},
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{
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"version": "6.12.112",
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"lessThanOrEqual": "6.12.*",
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"status": "unaffected",
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},
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{
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"version": "6.18.54",
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"status": "unaffected",
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"version": "7.2.8",
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"version": "7.3",
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"status": "unaffected",
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"url": "https://git.kernel.org/stable/c/acb03d3881818581052924a9bbbe92b8741ed448"
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}
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