---
cve: "CVE-2026-46242"
severity: "HIGH"
cvss: 7.8
epss: "3.2%"
vendor: "Linux"
kev: false
exploited: false
published: "2026-05-30 13:16:21"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-10T09:22:04+02:00"
---

# CVE-2026-46242

> 7.8 HIGH

## Beschreibung

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.

## CVSS-Vektor

```
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Lokal | good |
| AC Komplexität | Gering | bad |
| PR Privilegien | Gering | warn |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Hoch | bad |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Hoch | bad |

## Patch verfügbar (OSV)

- Kernel ≥ 6.1.178
- Kernel ≥ 6.6.144
- Kernel ≥ 6.12.95
- Kernel ≥ 6.18.33
- Kernel ≥ 7.0.10

## Referenzen

- <https://git.kernel.org/stable/c/3e1144d2515d28e4312e663ea05eac203101491d>
- <https://git.kernel.org/stable/c/2de4db145b2992da496fea6c51f9839be678ae24>
- <https://git.kernel.org/stable/c/9324de74a3a59b9fde9b62ee45ebaa71458ba2e5>
- <https://git.kernel.org/stable/c/ef4ca02e95363e78977ca04340d44fe3b4b2b81f>
- <https://git.kernel.org/stable/c/ced39b6a8062bac5c18a1c3df85634107eb8664a>
- <https://git.kernel.org/stable/c/a6dc643c69311677c574a0f17a3f4d66a5f3744b>
- <http://www.openwall.com/lists/oss-security/2026/07/08/14>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-46242) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_