CVE-2026-46242

eventpoll: fix ep_remove struct eventpoll / struct file UAF

Published May 30, 2026 CVSS 3.1 · 7.8 High EPSS 4.6% KEV · Not listed

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.

Analysis

Technical impact

The vulnerability is a use‑after‑free in the Linux kernel’s epoll handling. During a call to ep_remove, the function clears the file->f_ep field and then continues to use the now‑NULL @file within a critical section. A concurrent reference‑count drop frees the file and its associated eventpoll structure while the removal routine still holds a reference, enabling a kmem_cache_free on freed memory. The freed memory can then be overwritten, leading to kernel memory corruption.

Affected Systems

The flaw affects the Linux kernel itself, irrespective of distribution. All kernel versions compiled from source prior to the application of the patch are potentially vulnerable; the exact release numbers are not listed in the provided data. The issue arises in any build where the epoll subsystem is compiled and used.

Risk and Exploitability

EPSS is 4%, indicating a lower likelihood of exploitation, while the CVSS score remains 7.8, signalling medium severity. The vulnerability is not listed in CISA KEV. The description indicates a use‑after‑free that may be triggered by a race condition; however, the specific attack vector and necessary user privileges are not provided in the payload. It is inferred that a local user with the ability to manipulate epoll watches might be able to create such a race, but this is not explicitly confirmed. Successful exploitation could result in kernel memory corruption, potentially causing denial of service. No public exploitation data is available.

Affected Products

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

Linux

unaffected

Version	Status	Constraints
`f2451def095c1743adcfcb0cb5dadc86034e162a`	affected	< a10fbbe74e1c743beb1bb312109366667461df8a
`a1f93804449d13f97dabd4b996817de4bf1ed67a`	affected	< 3e1144d2515d28e4312e663ea05eac203101491d
`58c9b016e12855286370dfb704c08498edbc857a`	affected	< 2de4db145b2992da496fea6c51f9839be678ae24
`58c9b016e12855286370dfb704c08498edbc857a`	affected	< 9324de74a3a59b9fde9b62ee45ebaa71458ba2e5
`58c9b016e12855286370dfb704c08498edbc857a`	affected	< ef4ca02e95363e78977ca04340d44fe3b4b2b81f
`58c9b016e12855286370dfb704c08498edbc857a`	affected	< ced39b6a8062bac5c18a1c3df85634107eb8664a
`58c9b016e12855286370dfb704c08498edbc857a`	affected	< a6dc643c69311677c574a0f17a3f4d66a5f3744b
`5.15.209`	affected	< 5.15.222
`6.1.175`	affected	< 6.1.178

Linux

affected

Version	Status	Constraints
`6.4`	affected	—
`0`	unaffected	< 6.4
`5.15.222`	unaffected	≤ 5.15.*
`6.1.178`	unaffected	≤ 6.1.*
`6.6.144`	unaffected	≤ 6.6.*
`6.12.95`	unaffected	≤ 6.12.*
`6.18.33`	unaffected	≤ 6.18.*
`7.0.10`	unaffected	≤ 7.0.*
`7.1`	unaffected	≤ *

Configuration 1 [-]

OR	cpe:2.3:o:linux:linux_kernel::::::::
	cpe:2.3:o:linux:linux_kernel::::::::
	cpe:2.3:o:linux:linux_kernel::::::::
	cpe:2.3:o:linux:linux_kernel::::::::

No data.

Vendor Product Versions

Linux

Linux Kernel

Version	Status	Scheme	Platform
`[58c9b016e12855286370dfb704c08498edbc857a,ef4ca02e95363e78977ca04340d44fe3b4b2b81f)`	affected	code_commit	—
`[58c9b016e12855286370dfb704c08498edbc857a,ced39b6a8062bac5c18a1c3df85634107eb8664a)`	affected	code_commit	—
`[58c9b016e12855286370dfb704c08498edbc857a,a6dc643c69311677c574a0f17a3f4d66a5f3744b)`	affected	code_commit	—

Linux

Linux Kernel

Version	Status	Scheme	Platform
`6.4`	affected	generic	—
`[0,6.4)`	unaffected	generic	—
`[6.18.33,6.19.0)`	unaffected	semver	—
`[7.0.10,7.1.0)`	unaffected	semver	—
`[7.1-rc1,*]`	unaffected	generic	—

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

Apply the latest Linux kernel patch that fixes the ep_remove use‑after‑free and reboot
If an immediate kernel upgrade is not possible, disable or restrict access to the epoll interface or stop services that use it to eliminate the attack surface
Enable kernel hardening mitigations such as KASLR, SLUB randomization, mandatory access control (SELinux/AppArmor), and monitor system logs for EPOLL‑related crashes, applying subsequent security updates promptly

Generated by OpenCVE AI on October 17, 2026 at 10:11 UTC.

Tracking

Advisories

Source	ID	Title
Debian DSA	DSA-6381-1	linux security update
Ubuntu USN	USN-8566-1	Linux kernel vulnerabilities
Ubuntu USN	USN-8568-1	Linux kernel (OEM) vulnerabilities
Ubuntu USN	USN-8569-1	Linux kernel (HWE) vulnerabilities
Ubuntu USN	USN-8593-1	Linux kernel vulnerabilities
Ubuntu USN	USN-8603-1	Linux kernel (Azure) vulnerabilities
Ubuntu USN	USN-8618-1	Linux kernel vulnerabilities
Ubuntu USN	USN-8630-1	Linux kernel vulnerabilities
Ubuntu USN	USN-8636-1	Linux kernel vulnerabilities
Ubuntu USN	USN-8630-2	Linux kernel vulnerabilities
Ubuntu USN	USN-8630-3	Linux kernel (Oracle) vulnerabilities
Ubuntu USN	USN-8636-2	Linux kernel (Oracle) vulnerabilities
Ubuntu USN	USN-8656-1	Linux kernel (HWE) vulnerabilities
Ubuntu USN	USN-8630-4	Linux kernel (AWS) vulnerabilities
Ubuntu USN	USN-8663-1	Linux kernel (NVIDIA) vulnerabilities
Ubuntu USN	USN-8664-1	Linux kernel (NVIDIA BaseOS) vulnerabilities
Ubuntu USN	USN-8669-1	Linux kernel (NVIDIA) vulnerabilities
Ubuntu USN	USN-8630-5	Linux kernel (Raspberry Pi) vulnerabilities
Ubuntu USN	USN-8728-1	Linux kernel (GCP) vulnerabilities
Ubuntu USN	USN-8728-2	Linux kernel (Azure) vulnerabilities
Ubuntu USN	USN-8728-3	Linux kernel (Oracle) vulnerabilities
Ubuntu USN	USN-8961-1	Linux kernel vulnerabilities
Ubuntu USN	USN-9029-1	Linux kernel (Raspberry Pi) vulnerabilities

Metrics

No CVSS v4.0

Attack Vector Local

Attack Complexity Low

Privileges Required Low

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploit prediction score: 4.6% (4.576% probability within 30 days)

Exploitation none

Automatable no

Technical Impact total

References

Link	Providers
http://www.openwall.com/lists/oss-security/2026/07/08/14
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
https://git.kernel.org/stable/c/ced39b6a8062bac5c18a1c3df85634107eb8664a
https://git.kernel.org/stable/c/ef4ca02e95363e78977ca04340d44fe3b4b2b81f
https://lore.kernel.org/linux-cve-announce/2026053014-CVE-2026-46242-8394@gregkh/T
https://nvd.nist.gov/vuln/detail/CVE-2026-46242
https://www.cve.org/CVERecord?id=CVE-2026-46242

History

Nov 10, 2026 9:30 PM Scoring metrics updated View changes

Type	Values Removed	Values Added
Metrics		ssvc `{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}`

Oct 3, 2026 11:15 AM Added references View changes

Type	Values Removed	Values Added
References		https://git.kernel.org/stable/c/a10fbbe74e1c743beb1bb312109366667461df8a

Jul 24, 2026 6:30 PM Added references View changes

Type	Values Removed	Values Added
References		https://git.kernel.org/stable/c/3e1144d2515d28e4312e663ea05eac203101491d

Jul 4, 2026 12:15 PM Added references View changes

Type	Values Removed	Values Added
References		https://git.kernel.org/stable/c/2de4db145b2992da496fea6c51f9839be678ae24 https://git.kernel.org/stable/c/9324de74a3a59b9fde9b62ee45ebaa71458ba2e5

Jun 10, 2026 9:30 PM Weaknesses updated View changes

Type	Values Removed	Values Added
Weaknesses		CWE-416

Jun 5, 2026 6:45 AM Scoring metrics updated View changes

Type	Values Removed	Values Added
Metrics	cvssV3_1 `{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}`	cvssV3_1 `{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}`

Jun 2, 2026 1:30 PM Weaknesses updated View changes

Type	Values Removed	Values Added
Weaknesses	CWE-416

Jun 2, 2026 12:15 PM Weaknesses updated. Added references. Scoring metrics updated View changes

Type	Values Removed	Values Added
Weaknesses		CWE-825
References		https://lore.kernel.org/linux-cve-announce/2026053014-CVE-2026-46242-8394@gregkh/T https://nvd.nist.gov/vuln/detail/CVE-2026-46242 https://www.cve.org/CVERecord?id=CVE-2026-46242
Metrics	threat_severity `None`	cvssV3_1 `{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}` threat_severity `Moderate`

May 30, 2026 2:15 PM Weaknesses updated View changes

Type	Values Removed	Values Added
Weaknesses		CWE-416

May 30, 2026 12:45 PM Description updated. Title updated. First appearance in the feed. Affected versions updated. Affected vendors updated. Added references View changes

Type	Values Removed	Values Added
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.
Title		eventpoll: fix ep_remove struct eventpoll / struct file UAF
First Time appeared		Linux Linux linux Kernel
CPEs		cpe:2.3:o:linux:linux_kernel::::::::
Vendors & Products		Linux Linux linux Kernel
References		https://git.kernel.org/stable/c/a6dc643c69311677c574a0f17a3f4d66a5f3744b https://git.kernel.org/stable/c/ced39b6a8062bac5c18a1c3df85634107eb8664a https://git.kernel.org/stable/c/ef4ca02e95363e78977ca04340d44fe3b4b2b81f