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Full vulnerability report · 2024
CVE-2021-47461High confidence

userfaultfd: fix a race between writeprotect and exit_mmap()

Linux · Linux

7.8HighCVSS 3.1
Recommended action
Within 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Select the national-authority views to include. The exact source language is shown on each matched advisory. Your choice is remembered on this device and encoded in the shareable URL.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2021-34466

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

In the Linux kernel, the following vulnerability has been resolved: userfaultfd: fix a race between writeprotect and exit_mmap() A race is possible when a process exits, its VMAs are removed by exit_mmap() and at the same time userfaultfd_writeprotect() is called. The race was detected by KASAN on a development kernel, but it appears to be possible on vanilla kernels as well. Use mmget_not_zero() to prevent the race as done in other userfaultfd operations.

What

In the Linux kernel, the following vulnerability has been resolved: userfaultfd: fix a race between writeprotect and exit_mmap() A race is possible when a process exits, its VMAs are removed by exit_mmap() and at the same time userfaultfd_writeprotect() is called. The race was detected by KASAN on a development kernel, but it appears to be possible on vanilla kernels as well. Use mmget_not_zero() to prevent the race as done in other userfaultfd operations.

Why

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

How

An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

In the Linux kernel, the following vulnerability has been resolved: userfaultfd: fix a race between writeprotect and exit_mmap() A race is possible when a process exits, its VMAs are removed by exit_mmap() and at the same time userfaultfd_writeprotect() is called. The race was detected by KASAN on a development kernel, but it appears to be possible on vanilla kernels as well. Use mmget_not_zero() to prevent the race as done in other userfaultfd operations.

Why

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

How

An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
local access → Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Local
Privileges required
Low: a basic authenticated account is required
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-362

CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition'). The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVLocalAttack vector: The attacker needs local access to the vulnerable system.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRLowPrivileges required: The attacker needs basic user-level privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
The issue can support a local privilege or sandbox boundary transition; normal system utilities may then be available in the gained context.
CWE-362
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

BSI · German · WID-SEC-W-2024-1913Red Hat OpenShift Container Platform: Mehrere Schwachstellen

Ein entfernter anonymer oder lokaler Angreifer kann mehrere Schwachstellen in Red Hat OpenShift Container Platform ausnutzen, um seine Privilegien zu erhöhen, beliebigen Code auszuführen, einen Denial-of-Service-Zustand zu erzeugen, vertrauliche Informationen offenzulegen, Dateien und Daten zu manipulieren oder Sicherheitsmaßnahmen zu umgehen.

Official advisory
BSI · German · WID-SEC-W-2024-1197Linux Kernel: Mehrere Schwachstellen ermöglichen Denial of Service und unspezifische Angriffe

Ein lokaler Angreifer kann mehrere Schwachstellen im Linux-Kernel ausnutzen, um einen Denial-of-Service-Zustand zu erzeugen oder unspezifische Angriffe durchzuführen.

Official advisory
CERT-FR · French · CERTFR-2025-AVI-0072Multiples vulnérabilités dans Juniper Secure Analytics

mand-JSA-Series-Multiple-vulnerabilities-resolved-in-Juniper-Secure-Analytics-in-7-5-0-UP10-IF02 Référence CVE CVE-2021-46939 https://www.cve.org/CVERecord?id=CVE-2021-46939 Référence CVE CVE-2021-47018 https://www.cve.org/CVERecord?id=CVE-2021-47018 Référence CVE CVE-2021-47257 https://www.cve.org/CVERecord?id=CVE-2021-47257 Référence CVE CVE-2021-47284 https://www.cve.org/CVERecord?id=CVE-2021-47284 Référence CVE CVE-2021-47304 https://www.cve.org/CVERecord?id=CVE-2021-47304 Référence CVE CVE-2021-47373 https://www.cve.org/CVERecord?id=CVE-2021-47373 Référence CVE CVE-2021-47408 https://www.cve.org/CVERecord?id=CVE-2021-47408 Référence CVE CVE-2021-47461 https://www.cve.org/CVERecord?id=CVE-2021-47461 Référence CVE CVE-2021-47468 https://www.cve.org/CVERecord?id=CVE-2021-47468 Référence CVE CVE-2021-47491 https://www.cve.org/CVERecord?id=CVE-2021-47491 Référence CVE CVE-2021-47548 https://www.cve.org/CVERecord?id=CVE-2021-47548 Référence CVE CVE-2021-47579 https://www.cve.org/CVERecord?id=CVE-2021-47579 Référence CVE CVE-2021-47624 https://www.cve.org/CVERecord?id=CVE-2021-47624 Référence CVE CVE-2022-48632 https://www.cve.org/CVERecord?id=CVE-2022-48632 Référence CVE CVE-2022-48743 https://www.cve.org/CVERecord?id=CVE-2022-48743 Référence CVE CVE-2022-48747 https://www.cve.org/CVERecord?id=

Official advisory
CERT-FR · French · CERTFR-2024-AVI-1032Multiples vulnérabilités dans le noyau Linux de Red Hat

.com/errata/RHSA-2024:10273 Bulletin de sécurité Red Hat RHSA-2024:10274 du 26 novembre 2024 https://access.redhat.com/errata/RHSA-2024:10274 Bulletin de sécurité Red Hat RHSA-2024:10275 du 26 novembre 2024 https://access.redhat.com/errata/RHSA-2024:10275 Bulletin de sécurité Red Hat RHSA-2024:10281 du 26 novembre 2024 https://access.redhat.com/errata/RHSA-2024:10281 Bulletin de sécurité Red Hat RHSA-2024:10282 du 26 novembre 2024 https://access.redhat.com/errata/RHSA-2024:10282 Référence CVE CVE-2021-4204 https://www.cve.org/CVERecord?id=CVE-2021-4204 Référence CVE CVE-2021-47393 https://www.cve.org/CVERecord?id=CVE-2021-47393 Référence CVE CVE-2021-47461 https://www.cve.org/CVERecord?id=CVE-2021-47461 Référence CVE CVE-2022-0500 https://www.cve.org/CVERecord?id=CVE-2022-0500 Référence CVE CVE-2022-23222 https://www.cve.org/CVERecord?id=CVE-2022-23222 Référence CVE CVE-2022-48686 https://www.cve.org/CVERecord?id=CVE-2022-48686 Référence CVE CVE-2022-48773 https://www.cve.org/CVERecord?id=CVE-2022-48773 Référence CVE CVE-2022-48786 https://www.cve.org/CVERecord?id=CVE-2022-48786 Référence CVE CVE-2022-48929 https://www.cve.org/CVERecord?id=CVE-2022-48929 Référence CVE CVE-2023-0597 https://www.cve.org/CVERecord?id=CVE-2023-0597 Référence CVE CVE-2023-52489 https://www.cve.org/CVERecord?id=CVE-

Official advisory
CERT-FR · French · CERTFR-2024-AVI-0958Multiples vulnérabilités dans les produits IBM

d?id=CVE-2021-46939 Référence CVE CVE-2021-47018 https://www.cve.org/CVERecord?id=CVE-2021-47018 Référence CVE CVE-2021-47231 https://www.cve.org/CVERecord?id=CVE-2021-47231 Référence CVE CVE-2021-47257 https://www.cve.org/CVERecord?id=CVE-2021-47257 Référence CVE CVE-2021-47284 https://www.cve.org/CVERecord?id=CVE-2021-47284 Référence CVE CVE-2021-47304 https://www.cve.org/CVERecord?id=CVE-2021-47304 Référence CVE CVE-2021-47373 https://www.cve.org/CVERecord?id=CVE-2021-47373 Référence CVE CVE-2021-47408 https://www.cve.org/CVERecord?id=CVE-2021-47408 Référence CVE CVE-2021-47449 https://www.cve.org/CVERecord?id=CVE-2021-47449 Référence CVE CVE-2021-47461 https://www.cve.org/CVERecord?id=CVE-2021-47461 Référence CVE CVE-2021-47468 https://www.cve.org/CVERecord?id=CVE-2021-47468 Référence CVE CVE-2021-47491 https://www.cve.org/CVERecord?id=CVE-2021-47491 Référence CVE CVE-2021-47548 https://www.cve.org/CVERecord?id=CVE-2021-47548 Référence CVE CVE-2021-47579 https://www.cve.org/CVERecord?id=CVE-2021-47579 Référence CVE CVE-2021-47624 https://www.cve.org/CVERecord?id=CVE-2021-47624 Référence CVE CVE-2022-23181 https://www.cve.org/CVERecord?id=CVE-2022-23181 Référence CVE CVE-2022-23471 https://www.cve.org/CVERecord?id=CVE-2022-23471 Référence CVE CVE-2022-23648 https://www.cve.org/CVERecord?id=

Official advisory
CERT-FR · French · CERTFR-2024-AVI-0668Multiples vulnérabilités dans le noyau Linux de Red Hat

rata/RHSA-2024:5102 Référence CVE CVE-2021-46939 https://www.cve.org/CVERecord?id=CVE-2021-46939 Référence CVE CVE-2021-47018 https://www.cve.org/CVERecord?id=CVE-2021-47018 Référence CVE CVE-2021-47257 https://www.cve.org/CVERecord?id=CVE-2021-47257 Référence CVE CVE-2021-47284 https://www.cve.org/CVERecord?id=CVE-2021-47284 Référence CVE CVE-2021-47304 https://www.cve.org/CVERecord?id=CVE-2021-47304 Référence CVE CVE-2021-47373 https://www.cve.org/CVERecord?id=CVE-2021-47373 Référence CVE CVE-2021-47393 https://www.cve.org/CVERecord?id=CVE-2021-47393 Référence CVE CVE-2021-47408 https://www.cve.org/CVERecord?id=CVE-2021-47408 Référence CVE CVE-2021-47461 https://www.cve.org/CVERecord?id=CVE-2021-47461 Référence CVE CVE-2021-47468 https://www.cve.org/CVERecord?id=CVE-2021-47468 Référence CVE CVE-2021-47491 https://www.cve.org/CVERecord?id=CVE-2021-47491 Référence CVE CVE-2021-47548 https://www.cve.org/CVERecord?id=CVE-2021-47548 Référence CVE CVE-2021-47579 https://www.cve.org/CVERecord?id=CVE-2021-47579 Référence CVE CVE-2021-47624 https://www.cve.org/CVERecord?id=CVE-2021-47624 Référence CVE CVE-2022-48632 https://www.cve.org/CVERecord?id=CVE-2022-48632 Référence CVE CVE-2022-48637 https://www.cve.org/CVERecord?id=CVE-2022-48637 Référence CVE CVE-2022-48743 https://www.cve.org/CVERecord?id=

Official advisory
CERT-FR · French · CERTFR-2024-AVI-0526Multiples vulnérabilités dans le noyau Linux de SUSE

d?id=CVE-2021-47452 Référence CVE CVE-2021-47453 https://www.cve.org/CVERecord?id=CVE-2021-47453 Référence CVE CVE-2021-47454 https://www.cve.org/CVERecord?id=CVE-2021-47454 Référence CVE CVE-2021-47455 https://www.cve.org/CVERecord?id=CVE-2021-47455 Référence CVE CVE-2021-47456 https://www.cve.org/CVERecord?id=CVE-2021-47456 Référence CVE CVE-2021-47457 https://www.cve.org/CVERecord?id=CVE-2021-47457 Référence CVE CVE-2021-47458 https://www.cve.org/CVERecord?id=CVE-2021-47458 Référence CVE CVE-2021-47459 https://www.cve.org/CVERecord?id=CVE-2021-47459 Référence CVE CVE-2021-47460 https://www.cve.org/CVERecord?id=CVE-2021-47460 Référence CVE CVE-2021-47461 https://www.cve.org/CVERecord?id=CVE-2021-47461 Référence CVE CVE-2021-47462 https://www.cve.org/CVERecord?id=CVE-2021-47462 Référence CVE CVE-2021-47463 https://www.cve.org/CVERecord?id=CVE-2021-47463 Référence CVE CVE-2021-47464 https://www.cve.org/CVERecord?id=CVE-2021-47464 Référence CVE CVE-2021-47465 https://www.cve.org/CVERecord?id=CVE-2021-47465 Référence CVE CVE-2021-47466 https://www.cve.org/CVERecord?id=CVE-2021-47466 Référence CVE CVE-2021-47467 https://www.cve.org/CVERecord?id=CVE-2021-47467 Référence CVE CVE-2021-47468 https://www.cve.org/CVERecord?id=CVE-2021-47468 Référence CVE CVE-2021-47469 https://www.cve.org/CVERecord?id=

Official advisory
CERT-FR · French · CERTFR-2024-AVI-0496Multiples vulnérabilités dans le noyau Linux de SUSE

d?id=CVE-2021-47452 Référence CVE CVE-2021-47453 https://www.cve.org/CVERecord?id=CVE-2021-47453 Référence CVE CVE-2021-47454 https://www.cve.org/CVERecord?id=CVE-2021-47454 Référence CVE CVE-2021-47455 https://www.cve.org/CVERecord?id=CVE-2021-47455 Référence CVE CVE-2021-47456 https://www.cve.org/CVERecord?id=CVE-2021-47456 Référence CVE CVE-2021-47457 https://www.cve.org/CVERecord?id=CVE-2021-47457 Référence CVE CVE-2021-47458 https://www.cve.org/CVERecord?id=CVE-2021-47458 Référence CVE CVE-2021-47459 https://www.cve.org/CVERecord?id=CVE-2021-47459 Référence CVE CVE-2021-47460 https://www.cve.org/CVERecord?id=CVE-2021-47460 Référence CVE CVE-2021-47461 https://www.cve.org/CVERecord?id=CVE-2021-47461 Référence CVE CVE-2021-47462 https://www.cve.org/CVERecord?id=CVE-2021-47462 Référence CVE CVE-2021-47463 https://www.cve.org/CVERecord?id=CVE-2021-47463 Référence CVE CVE-2021-47464 https://www.cve.org/CVERecord?id=CVE-2021-47464 Référence CVE CVE-2021-47465 https://www.cve.org/CVERecord?id=CVE-2021-47465 Référence CVE CVE-2021-47466 https://www.cve.org/CVERecord?id=CVE-2021-47466 Référence CVE CVE-2021-47467 https://www.cve.org/CVERecord?id=CVE-2021-47467 Référence CVE CVE-2021-47468 https://www.cve.org/CVERecord?id=CVE-2021-47468 Référence CVE CVE-2021-47469 https://www.cve.org/CVERecord?id=

Official advisory
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
63b2d4174c4ad1f40b48d7138e71bcb564c1fe03 < 3cda4bfffd4f755645577aaa9e96a606657b4525; 63b2d4174c4ad1f40b48d7138e71bcb564c1fe03 < 149958ecd0627a9f1e9c678c25c665400054cd6a; 63b2d4174c4ad1f40b48d7138e71bcb564c1fe03 < cb185d5f1ebf900f4ae3bf84cee212e6dd035aca; 5.7
Fixed
< 5.7; 5.10.76 ≤ 5.10.*; 5.14.15 ≤ 5.14.*; 5.15 ≤ *
Action
Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
Workaround
No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04

Evidence and provenance

Published 22 May 2024 · Last source change 5 Aug 2026, 08:47 UTC · CWE-362 · Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2021-34466
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceNIST NVD
NVD statusNVD modified after enrichment

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates →

No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.

Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2021-47461 · cve.blacktree.nl