CyberSecBulletin
CVE-2026-46242NVD status: Modified

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2026-46242 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions a10fbbe74e1c743beb1bb312109366667461df8a, 3e1144d2515d28e4312e663ea05eac203101491d, 2de4db145b2992da496fea6c51f9839be678ae24 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 4.58% chance of exploitation within 30 days, which is in the top 8.23% of all scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to a10fbbe74e1c743beb1bb312109366667461df8a or 3e1144d2515d28e4312e663ea05eac203101491d or 2de4db145b2992da496fea6c51f9839be678ae24 or 9324de74a3a59b9fde9b62ee45ebaa71458ba2e5, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.16 or 6.2 or 6.18.33 or 7.0.10, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxf2451def095c1743adcfcb0cb5dadc86034e162a up to, but not including, a10fbbe74e1c743beb1bb312109366667461df8a; a1f93804449d13f97dabd4b996817de4bf1ed67a up to, but not including, 3e1144d2515d28e4312e663ea05eac203101491d; 58c9b016e12855286370dfb704c08498edbc857a up to, but not including, 2de4db145b2992da496fea6c51f9839be678ae24; 58c9b016e12855286370dfb704c08498edbc857a up to, but not including, 9324de74a3a59b9fde9b62ee45ebaa71458ba2e5; 58c9b016e12855286370dfb704c08498edbc857a up to, but not including, ef4ca02e95363e78977ca04340d44fe3b4b2b81f; 58c9b016e12855286370dfb704c08498edbc857a up to, but not including, ced39b6a8062bac5c18a1c3df85634107eb8664a; 58c9b016e12855286370dfb704c08498edbc857a up to, but not including, a6dc643c69311677c574a0f17a3f4d66a5f3744b; 5.15.209 up to, but not including, 5.15.222; and 2 more rangesa10fbbe74e1c743beb1bb312109366667461df8a, 3e1144d2515d28e4312e663ea05eac203101491d, 2de4db145b2992da496fea6c51f9839be678ae24, 9324de74a3a59b9fde9b62ee45ebaa71458ba2e5, ef4ca02e95363e78977ca04340d44fe3b4b2b81f, ced39b6a8062bac5c18a1c3df85634107eb8664a
LinuxLinux Kernel5.15.209 up to, but not including, 5.16; 6.1.175 up to, but not including, 6.2; 6.4 up to, but not including, 6.18.33; 6.19 up to, but not including, 7.0.105.16, 6.2, 6.18.33, 7.0.10

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.

Official description

In the Linux kernel, the following vulnerability has been resolved: eventpoll: fix ep_remove struct eventpoll / struct file UAF ep_remove() (via ep_remove_file()) cleared file->f_ep under file->f_lock but then kept using @file inside the critical section (is_file_epoll(), hlist_del_rcu() through the head, spin_unlock). A concurrent __fput() taking the eventpoll_release() fastpath in that window observed the transient NULL, skipped eventpoll_release_file() and ran to f_op->release / file_free(). For the epoll-watches-epoll case, f_op->release is ep_eventpoll_release() -> ep_clear_and_put() -> ep_free(), which kfree()s the watched struct eventpoll. Its embedded ->refs hlist_head is exactly where epi->fllink.pprev points, so the subsequent hlist_del_rcu()'s "*pprev = next" scribbles into freed kmalloc-192 memory. In addition, struct file is SLAB_TYPESAFE_BY_RCU, so the slot backing @file could be recycled by alloc_empty_file() -- reinitializing f_lock and f_ep -- while ep_remove() is still nominally inside that lock. The upshot is an attacker-controllable kmem_cache_free() against the wrong slab cache. Pin @file via epi_fget() at the top of ep_remove() and gate the critical section on the pin succeeding. With the pin held @file cannot reach refcount zero, which holds __fput() off and transitively keeps the watched struct eventpoll alive across the hlist_del_rcu() and the f_lock use, closing both UAFs. If the pin fails @file has already reached refcount zero and its __fput() is in flight. Because we bailed before clearing f_ep, that path takes the eventpoll_release() slow path into eventpoll_release_file() and blocks on ep->mtx until the waiter side's ep_clear_and_put() drops it. The bailed epi's share of ep->refcount stays intact, so the trailing ep_refcount_dec_and_test() in ep_clear_and_put() cannot free the eventpoll out from under eventpoll_release_file(); the orphaned epi is then cleaned up there. A successful pin also proves we are not racing eventpoll_release_file() on this epi, so drop the now-redundant re-check of epi->dying under f_lock. The cheap lockless READ_ONCE(epi->dying) fast-path bailout stays.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Use After Free

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.

How developers prevent this class of flaw

  • Choose a language that provides automatic memory management.
  • When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.

More Use After Free vulnerabilities (CWE-416)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Use After Free vulnerabilities

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