CVE-2025-21984

Local kernel compromise via stale swapcache folio index

Published Apr 1, 2025 · Updated Aug 5, 2026

Race condition in the Linux kernel allows local users to crash the system or corrupt kernel memory through UFFDIO_MOVE. move_swap_pte() copies a swap PTE without updating the swap-cached folio index for the destination VMA, so do_swap_page() later observes inconsistent reverse-mapping metadata. Exploitation requires local syscall access, swap-cache timing, and attacker-controlled page activity; KSM state determines whether the result is a kernel BUG or silent memory corruption.

CVSS severity7.8
High
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Race condition in the Linux kernel allows local users to crash the system or corrupt kernel memory through UFFDIO_MOVE. move_swap_pte() copies a swap PTE without updating the swap-cached folio index for the destination VMA, so do_swap_page() later observes inconsistent reverse-mapping metadata. Exploitation requires local syscall access, swap-cache timing, and attacker-controlled page activity; KSM state determines whether the result is a kernel BUG or silent memory corruption.

The record

CVE
CVE-2025-21984
Published
Apr 1, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 1, 2025CVE 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

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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=6.8
  2. Affected versionversion=adef440691bab824e39c1b17382322d195e1fab0 <4e9507246298fd6f1ca7bb42ef01a6e34fb93684
  3. Affected versionversion=adef440691bab824e39c1b17382322d195e1fab0 <b1e11bd86c0943bb7624efebdc384340a50ad683
  4. Affected versionversion=adef440691bab824e39c1b17382322d195e1fab0 <c50f8e6053b0503375c2975bf47f182445aebb4c

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.8; version=adef440691bab824e39c1b17382322d195e1fab0 <4e9507246298fd6f1ca7bb42ef01a6e34fb93684; version=adef440691bab824e39c1b17382322d195e1fab0 <b1e11bd86c0943bb7624efebdc384340a50ad683; version=adef440691bab824e39c1b17382322d195e1fab0 <c50f8e6053b0503375c2975bf47f182445aebb4c

Published CVSS scores

7.8LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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

T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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