{"cve":"CVE-2026-46242","nvd":{"published":"2026-05-30T13:16:21.980","modified":"2026-10-19T20:18:39.123","status":"Modified","description":"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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8},"cwes":["CWE-416"],"references":["https://git.kernel.org/stable/c/2de4db145b2992da496fea6c51f9839be678ae24","https://git.kernel.org/stable/c/3e1144d2515d28e4312e663ea05eac203101491d","https://git.kernel.org/stable/c/9324de74a3a59b9fde9b62ee45ebaa71458ba2e5","https://git.kernel.org/stable/c/a10fbbe74e1c743beb1bb312109366667461df8a","https://git.kernel.org/stable/c/a6dc643c69311677c574a0f17a3f4d66a5f3744b"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-21T03:43:09.190223697+00:00"},"epss":{"cve":"CVE-2026-46242","score":0.0439,"percentile":0.91241,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}