CVE-2021-47461

Kernel crash via userfaultfd address-space race

Published May 22, 2024 · Updated Aug 5, 2026

Race condition in Linux 5.7 through 5.10.75, 5.11 through 5.14.14, and 5.15-rc1 through 5.15-rc6 allows local users to crash the kernel. userfaultfd_writeprotect passes its address space to mwriteprotect_range without first obtaining a nonzero mm reference, allowing exit_mmap to remove the target VMAs concurrently. Triggering requires local low-privileged access, a userfaultfd write-protection range, and concurrent process-exit and ioctl activity; the published NVD assessment limits demonstrated impact to availability.

CVSS severity4.7
Medium
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Race condition in Linux 5.7 through 5.10.75, 5.11 through 5.14.14, and 5.15-rc1 through 5.15-rc6 allows local users to crash the kernel. userfaultfd_writeprotect passes its address space to mwriteprotect_range without first obtaining a nonzero mm reference, allowing exit_mmap to remove the target VMAs concurrently. Triggering requires local low-privileged access, a userfaultfd write-protection range, and concurrent process-exit and ioctl activity; the published NVD assessment limits demonstrated impact to availability.

The record

CVE
CVE-2021-47461
Published
May 22, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-362, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 22, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.7
  2. Affected versionversion=63b2d4174c4ad1f40b48d7138e71bcb564c1fe03 <149958ecd0627a9f1e9c678c25c665400054cd6a
  3. Affected versionversion=63b2d4174c4ad1f40b48d7138e71bcb564c1fe03 <3cda4bfffd4f755645577aaa9e96a606657b4525
  4. Affected versionversion=63b2d4174c4ad1f40b48d7138e71bcb564c1fe03 <cb185d5f1ebf900f4ae3bf84cee212e6dd035aca

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.7; version=63b2d4174c4ad1f40b48d7138e71bcb564c1fe03 <149958ecd0627a9f1e9c678c25c665400054cd6a; version=63b2d4174c4ad1f40b48d7138e71bcb564c1fe03 <3cda4bfffd4f755645577aaa9e96a606657b4525; version=63b2d4174c4ad1f40b48d7138e71bcb564c1fe03 <cb185d5f1ebf900f4ae3bf84cee212e6dd035aca

Published CVSS scores

4.7NIST National Vulnerability DatabaseCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo