CVE-2025-21786

Local privilege escalation via rescuer pool use-after-free

Published Feb 27, 2025 · Updated Aug 5, 2026

Use-after-free in Linux kernel 6.11, 6.12 before 6.12.16, and 6.13 before 6.13.4 allows local users to elevate privileges. put_unbound_pool() releases the pool workqueue reference before worker_detach_from_pool() finishes detaching the rescuer, leaving freed pool state in use. Low-privilege local code can repeatedly create memory pressure and unbound WQ_MEM_RECLAIM work to reach the race, corrupt kernel memory, or crash the system without user interaction.

CVSS severity7.8
High
EPSS probability0.23%
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 6.11, 6.12 before 6.12.16, and 6.13 before 6.13.4 allows local users to elevate privileges. put_unbound_pool() releases the pool workqueue reference before worker_detach_from_pool() finishes detaching the rescuer, leaving freed pool state in use. Low-privilege local code can repeatedly create memory pressure and unbound WQ_MEM_RECLAIM work to reach the race, corrupt kernel memory, or crash the system without user interaction.

The record

CVE
CVE-2025-21786
Published
Feb 27, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416, T1499.004, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 27, 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

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=6.11
  2. Affected versionversion=68f83057b913467a999e1bf9e0da6a119668f769 <835b69c868f53f959d4986bbecd561ba6f38e492
  3. Affected versionversion=68f83057b913467a999e1bf9e0da6a119668f769 <e76946110137703c16423baf6ee177b751a34b7e
  4. Affected versionversion=68f83057b913467a999e1bf9e0da6a119668f769 <e7c16028a424dd35be1064a68fa318be4359310f

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.11; version=68f83057b913467a999e1bf9e0da6a119668f769 <835b69c868f53f959d4986bbecd561ba6f38e492; version=68f83057b913467a999e1bf9e0da6a119668f769 <e76946110137703c16423baf6ee177b751a34b7e; version=68f83057b913467a999e1bf9e0da6a119668f769 <e7c16028a424dd35be1064a68fa318be4359310f

Published CVSS scores

5.5SUSECVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
7.8Linux Kernel CNACVSS: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.

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-416Use After Free
T1499.004Application or System Exploitation
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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