314 lines
17 KiB
JSON
314 lines
17 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-2026-46242",
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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": "2026-05-13T15:03:33.107Z",
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"datePublished": "2026-05-30T12:13:45.594Z",
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"dateUpdated": "2026-10-19T19:36:55.705Z"
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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": "2026-10-03T10:55:32.867Z"
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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\neventpoll: fix ep_remove struct eventpoll / struct file UAF\n\nep_remove() (via ep_remove_file()) cleared file->f_ep under\nfile->f_lock but then kept using @file inside the critical section\n(is_file_epoll(), hlist_del_rcu() through the head, spin_unlock).\nA concurrent __fput() taking the eventpoll_release() fastpath in\nthat window observed the transient NULL, skipped\neventpoll_release_file() and ran to f_op->release / file_free().\n\nFor the epoll-watches-epoll case, f_op->release is\nep_eventpoll_release() -> ep_clear_and_put() -> ep_free(), which\nkfree()s the watched struct eventpoll. Its embedded ->refs\nhlist_head is exactly where epi->fllink.pprev points, so the\nsubsequent hlist_del_rcu()'s \"*pprev = next\" scribbles into freed\nkmalloc-192 memory.\n\nIn addition, struct file is SLAB_TYPESAFE_BY_RCU, so the slot\nbacking @file could be recycled by alloc_empty_file() --\nreinitializing f_lock and f_ep -- while ep_remove() is still\nnominally inside that lock. The upshot is an attacker-controllable\nkmem_cache_free() against the wrong slab cache.\n\nPin @file via epi_fget() at the top of ep_remove() and gate the\ncritical section on the pin succeeding. With the pin held @file\ncannot reach refcount zero, which holds __fput() off and\ntransitively keeps the watched struct eventpoll alive across the\nhlist_del_rcu() and the f_lock use, closing both UAFs.\n\nIf the pin fails @file has already reached refcount zero and its\n__fput() is in flight. Because we bailed before clearing f_ep,\nthat path takes the eventpoll_release() slow path into\neventpoll_release_file() and blocks on ep->mtx until the waiter\nside's ep_clear_and_put() drops it. The bailed epi's share of\nep->refcount stays intact, so the trailing ep_refcount_dec_and_test()\nin ep_clear_and_put() cannot free the eventpoll out from under\neventpoll_release_file(); the orphaned epi is then cleaned up\nthere.\n\nA successful pin also proves we are not racing\neventpoll_release_file() on this epi, so drop the now-redundant\nre-check of epi->dying under f_lock. The cheap lockless\nREAD_ONCE(epi->dying) fast-path bailout stays."
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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 - Exploitation requires local syscalls (`epoll_create1`, `epoll_ctl`, `close`) on nested epoll fds; there is no network, adjacent-radio, or physical-device path to the buggy `ep_remove`/`eventpoll_release` race.\nAC:L - An unprivileged attacker can drive both sides of the race (e.g., one thread `EPOLL_CTL_DEL` or closing the outer epoll while another closes the inner epoll fd) and retry until the transient `f_ep == NULL` window is hit, consistent with multi-threaded epoll workloads.\nPR:L - No capabilities or root are required; any local UID that may create epoll fds (including inside user namespaces/containers) can register nested epoll and trigger the concurrent remove/close paths.\nUI:N - No victim action is required beyond the attacker running their own concurrent epoll setup and close/DEL operations on the same host.\nS:U - Impact is kernel heap corruption and potential privilege escalation within the same kernel security domain, not a documented cross-boundary escape (e.g., guest-to-host or sandbox breakout).\nC:H - The bug is a use-after-free on `struct eventpoll` and potentially recycled `struct file` objects, which can be turned into arbitrary kernel memory disclosure via heap grooming and UAF reads.\nI:H - Concurrent teardown allows `hlist_del_rcu()` to write `*pprev` into freed kmalloc-192 memory and enables attacker-controllable `kmem_cache_free()` on the wrong cache, supporting arbitrary write/control-flow hijack primitives.\nA:H - The race causes invalid writes to freed memory and slab corruption, which routinely provokes kernel oops/panic or severe instability even when full exploitation is not attempted."
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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/eventpoll.c"
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],
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"status": "unaffected",
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},
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"version": "7.0.10",
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"lessThanOrEqual": "7.0.*",
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"status": "unaffected",
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"version": "7.1",
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"title": "eventpoll: fix ep_remove struct eventpoll / struct file UAF",
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}
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}
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