CVE-2025-21693

Local kernel compromise via CPU-hotplug use-after-free

Published Feb 10, 2025 · Updated Aug 5, 2026

Use-after-free in Linux kernel zswap 5.11 through 6.12.11 allows local users to corrupt kernel memory during CPU hot-unplug. zswap_compress() and zswap_decompress() retain a per-CPU acomp_ctx while execution can migrate, so zswap_cpu_comp_dead() can free its buffer, request, or compressor on the original CPU. Reaching the race requires zswap activity and a concurrent CPU-offline transition; successful reuse can disclose or corrupt kernel data, hijack control flow, or crash the host.

CVSS severity7.8
High
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Linux kernel zswap 5.11 through 6.12.11 allows local users to corrupt kernel memory during CPU hot-unplug. zswap_compress() and zswap_decompress() retain a per-CPU acomp_ctx while execution can migrate, so zswap_cpu_comp_dead() can free its buffer, request, or compressor on the original CPU. Reaching the race requires zswap activity and a concurrent CPU-offline transition; successful reuse can disclose or corrupt kernel data, hijack control flow, or crash the host.

The record

CVE
CVE-2025-21693
Published
Feb 10, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 10, 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=1ec3b5fe6eec782f4e5e0a80e4ce1909ffd5d161 <12dcb0ef540629a281533f9dedc1b6b8e14cfb65
  2. Affected versionversion=1ec3b5fe6eec782f4e5e0a80e4ce1909ffd5d161 <8d29ff5d50304daa41dc3cfdda4a9d1e46cf5be1
  3. Affected versionversion=5.11

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1ec3b5fe6eec782f4e5e0a80e4ce1909ffd5d161 <12dcb0ef540629a281533f9dedc1b6b8e14cfb65; version=1ec3b5fe6eec782f4e5e0a80e4ce1909ffd5d161 <8d29ff5d50304daa41dc3cfdda4a9d1e46cf5be1; version=5.11

Published CVSS scores

7.8Linux kernel security teamCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.0Amazon LinuxCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8UbuntuCVSS: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

CWE-416Use After Free
T1068Exploitation for Privilege Escalation

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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