Linux Kernel: Use After Free (CVE-2026-46242)

What is affected, what to do

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().

An exploit is publicly available. Update Linux Kernel to version 5.15.222, Linux Kernel to version 6.1.178, Linux Kernel to version 6.6.144.

Affected

• Linux Kernel lt 5.15.209..5.15.222
• Linux Kernel lt 6.1.175..6.1.178
• Linux Kernel lt 6.4..6.6.144
• Linux Kernel lt 6.7..6.12.95
• Linux Kernel lt 6.13..6.18.33
• Linux Kernel lt 6.19..7.0.10

Fixed in

• Linux Kernel 5.15.222
• Linux Kernel 6.1.178
• Linux Kernel 6.6.144
• Linux Kernel 6.12.95
• Linux Kernel 6.18.33
• Linux Kernel 7.0.10
• Linux Kernel 7.1

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Metrics

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2

NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

Read in glossary

High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.

CRA

The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

Read in glossary

From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.

ISO/IEC 27001

ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

Read in glossary

Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

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: HKCERT (CC BY 3.0 HK) · HKCERT rating: medium, suse_csaf, Ubuntu Security Notices, BSI WID Portal, BSI CSAF, redhat_csaf, Debian Security Advisories, OSV (Open Source Vulnerabilities), cvelistv5, NVD (NIST), Microsoft Security Update Guide, CVE.org (MITRE)

Vendors and products

• Android :linux Kernel:
• Debian Linux
• Google Google Android
• Google Android 14
• Google Android 15
• Google Android 16
• Google Android 17
• Google Android Automotive OS
• Google Android Xr
• IBM Datapower Gateway
• Linux Linux
• Linux Linux Kernel

Weakness classes (CWE)

• CWE-416Use After Free

  Variant

  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.

  Entry at MITRE CWE-416

References & sources

• git.kernel.orgstable/c/ef4ca02e95363e78977ca04340d44fe3b4b2b81fPatch
• git.kernel.orgstable/c/ced39b6a8062bac5c18a1c3df85634107eb8664aPatch
• git.kernel.orgstable/c/a6dc643c69311677c574a0f17a3f4d66a5f3744bPatch
• git.kernel.orgstable/c/3e1144d2515d28e4312e663ea05eac203101491d
• git.kernel.orgstable/c/2de4db145b2992da496fea6c51f9839be678ae24
• git.kernel.orgstable/c/9324de74a3a59b9fde9b62ee45ebaa71458ba2e5
• openwall.comlists/oss-security/2026/07/08/14
• git.kernel.orgstable/c/a10fbbe74e1c743beb1bb312109366667461df8a
• source.android.comsecurity/bulletin/2026-11-01advisory
• android.googlesource.comkernel/common/+/58c9b016e12855286370dfb704c08498edbc857afix
• android.googlesource.comkernel/common/+/4a33cb8c9fe2dd18962c39568401e35b5de0ae59fix
• android.googlesource.comkernel/common/+/c7a8aea27b87b74f62a2b2a5d16100caa2cba79cfix
• android.googlesource.comkernel/common/+/5255cec633890d782c8a1daf792801eb527d0ac8fix
• android.googlesource.comkernel/common/+/035da2cab032309d387d2935543743fb36c722c3fix
• android.googlesource.comkernel/common/+/59f29da4ef0793f38ad1dbc01a9ee11bd4df636cfix
• android.googlesource.comkernel/common/+/b51793e6880dff374dfcd95f8335bfa1e556fadbfix
• android.googlesource.comkernel/common/+/e0384993ef8206abe4e644c0cb4bdb59d2c7bb4bfix
• android.googlesource.comkernel/common/+/02f217a4bffc8a00313bf52ebb96003d7ae1d5d8fix
• android.googlesource.comkernel/common/+/500d67e5110ab44ec1501113db76aa07287c112bfix
• android.googlesource.comkernel/common/+/690d6106eec64f970d6b2bf87599838b016b1b00fix

Changes to this CVE

Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

1. 19.10.2026Record modifiedCISA ADP

   Weakness type: CWE-416

   Show the original change

   Individual changes of this event as published by NVD

   Type	Action	Before	After
   Weakness type (CWE)	added	—	CWE-416

   Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

2. 16.10.2026Record modifiedCISA ADP

   CISA assessment (SSVC): exploitation: none known, automatable: no

   Show the original change

   Individual changes of this event as published by NVD

   Type	Action	Before	After
   SSVC assessment	added	—	{"id":"CVE-2026-46242","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:21:18.370364Z"}

   Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

3. 03.10.2026Record modifiedLinux

   New 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

   and 3 more references

   Show 17 original changes

   Individual changes of this event as published by NVD

   Type	Action	Before	After
   Affected versions (publisher)	added	—	Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/46xxx/CVE-2026-46242.json">CVE-2026-46242</a>
   Reference	added	—	https://git.kernel.org/stable/c/2de4db145b2992da496fea6c51f9839be678ae24
   Reference	added	—	https://git.kernel.org/stable/c/3e1144d2515d28e4312e663ea05eac203101491d
   Reference	added	—	https://git.kernel.org/stable/c/9324de74a3a59b9fde9b62ee45ebaa71458ba2e5
   Reference	added	—	https://git.kernel.org/stable/c/a10fbbe74e1c743beb1bb312109366667461df8a
   Reference	added	—	https://git.kernel.org/stable/c/a6dc643c69311677c574a0f17a3f4d66a5f3744b
   Reference	added	—	https://git.kernel.org/stable/c/ced39b6a8062bac5c18a1c3df85634107eb8664a
   Reference	added	—	https://git.kernel.org/stable/c/ef4ca02e95363e78977ca04340d44fe3b4b2b81f
   Reference	removed	https://git.kernel.org/stable/c/2de4db145b2992da496fea6c51f9839be678ae24	—
   Reference	removed	https://git.kernel.org/stable/c/3e1144d2515d28e4312e663ea05eac203101491d	—
   Reference	removed	https://git.kernel.org/stable/c/9324de74a3a59b9fde9b62ee45ebaa71458ba2e5	—
   Reference	removed	https://git.kernel.org/stable/c/a6dc643c69311677c574a0f17a3f4d66a5f3744b	—
   Reference	removed	https://git.kernel.org/stable/c/ced39b6a8062bac5c18a1c3df85634107eb8664a	—
   Reference	removed	https://git.kernel.org/stable/c/ef4ca02e95363e78977ca04340d44fe3b4b2b81f	—
   Reference type	removed	https://git.kernel.org/stable/c/a6dc643c69311677c574a0f17a3f4d66a5f3744b Types: Patch	—
   Reference type	removed	https://git.kernel.org/stable/c/ced39b6a8062bac5c18a1c3df85634107eb8664a Types: Patch	—
   Reference type	removed	https://git.kernel.org/stable/c/ef4ca02e95363e78977ca04340d44fe3b4b2b81f Types: Patch	—

   Source identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

4. 03.10.2026Record modifiedCVE Program

   New references:

   • http://www.openwall.com/lists/oss-security/2026/07/08/14
   Show 2 original changes

   Individual changes of this event as published by NVD

   Type	Action	Before	After
   Reference	added	—	http://www.openwall.com/lists/oss-security/2026/07/08/14
   Reference	removed	http://www.openwall.com/lists/oss-security/2026/07/08/14	—

   Source identifier: af854a3a-2127-422b-91ae-364da2661108

5. 24.07.2026Record modifiedLinux

   New references:

   • https://git.kernel.org/stable/c/3e1144d2515d28e4312e663ea05eac203101491d
   Show 2 original changes

   Individual changes of this event as published by NVD

   Type	Action	Before	After
   Reference	added	—	https://git.kernel.org/stable/c/3e1144d2515d28e4312e663ea05eac203101491d
   Affected versions (publisher)	changed	Linux, Linux	Linux, Linux

   Source identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

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