CVE-2025-21696

Local service interruption via stale uffd-wp flags

Published Feb 12, 2025 · Updated May 11, 2026

State inconsistency in Linux 5.7 through 6.12.10 allows local users to interrupt service through userfaultfd and mremap operations. During mremap(), the kernel clears VM_UFFD_WP from the VMA but leaves uffd-wp set in PTE, swap-PTE, marker, huge-PMD, or hugetlb representations, so a later mprotect(PROT_WRITE) hits page_table_check_pte_flags(). Exploitation requires low-privileged local access and a write-protected userfaultfd region registered without UFFD_FEATURE_EVENT_REMAP; the documented consequence is an availability-impacting kernel warning.

CVSS severity5.5
Medium
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

State inconsistency in Linux 5.7 through 6.12.10 allows local users to interrupt service through userfaultfd and mremap operations. During mremap(), the kernel clears VM_UFFD_WP from the VMA but leaves uffd-wp set in PTE, swap-PTE, marker, huge-PMD, or hugetlb representations, so a later mprotect(PROT_WRITE) hits page_table_check_pte_flags(). Exploitation requires low-privileged local access and a write-protected userfaultfd region registered without UFFD_FEATURE_EVENT_REMAP; the documented consequence is an availability-impacting kernel warning.

The record

CVE
CVE-2025-21696
Published
Feb 12, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 12, 2025CVE publishedPublication date reported by the CVE source.
  2. May 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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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 <0cef0bb836e3cfe00f08f9606c72abd72fe78ca3
  3. Affected versionversion=63b2d4174c4ad1f40b48d7138e71bcb564c1fe03 <310ac886d68de661c3a334198d8604b722d7fdf8

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.7; version=63b2d4174c4ad1f40b48d7138e71bcb564c1fe03 <0cef0bb836e3cfe00f08f9606c72abd72fe78ca3; version=63b2d4174c4ad1f40b48d7138e71bcb564c1fe03 <310ac886d68de661c3a334198d8604b722d7fdf8

Published CVSS scores

5.5UbuntuCVSS:3.1/AV:L/AC:L/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.

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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

T1499Endpoint Denial of Service

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

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Your stack

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