CVE-2025-21918

Local system crash via premature UCSI cleanup

Published Apr 1, 2025 · Updated May 11, 2026

NULL pointer dereference in the Linux kernel UCSI subsystem allows local users to crash the system during UCSI resource teardown. The UCSI connector cleanup path deallocates resources before its asynchronous workqueue has finished, allowing worker code to access released state. Reachability requires local low-privileged access and the affected USB Type-C UCSI polling code; the bounded consequence is a kernel crash without reported data disclosure or modification.

CVSS severity5.5
Medium
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

NULL pointer dereference in the Linux kernel UCSI subsystem allows local users to crash the system during UCSI resource teardown. The UCSI connector cleanup path deallocates resources before its asynchronous workqueue has finished, allowing worker code to access released state. Reachability requires local low-privileged access and the affected USB Type-C UCSI polling code; the bounded consequence is a kernel crash without reported data disclosure or modification.

The record

CVE
CVE-2025-21918
Published
Apr 1, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-476, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 1, 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=5.16
  2. Affected versionversion=b9aa02ca39a49740926c2c450a1505a4a0f8954a <079a3e52f3e751bb8f5937195bdf25c5d14fdff0
  3. Affected versionversion=b9aa02ca39a49740926c2c450a1505a4a0f8954a <46fba7be161bb89068958138ea64ec33c0b446d4
  4. Affected versionversion=b9aa02ca39a49740926c2c450a1505a4a0f8954a <592a0327d026a122e97e8e8bb7c60cbbe7697344
  5. Affected versionversion=b9aa02ca39a49740926c2c450a1505a4a0f8954a <7a735a8a46f6ebf898bbefd96659ca5da798bce0
  6. Affected versionversion=b9aa02ca39a49740926c2c450a1505a4a0f8954a <b13abcb7ddd8d38de769486db5bd917537b32ab1

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.16; version=b9aa02ca39a49740926c2c450a1505a4a0f8954a <079a3e52f3e751bb8f5937195bdf25c5d14fdff0; version=b9aa02ca39a49740926c2c450a1505a4a0f8954a <46fba7be161bb89068958138ea64ec33c0b446d4; version=b9aa02ca39a49740926c2c450a1505a4a0f8954a <592a0327d026a122e97e8e8bb7c60cbbe7697344; version=b9aa02ca39a49740926c2c450a1505a4a0f8954a <7a735a8a46f6ebf898bbefd96659ca5da798bce0; version=b9aa02ca39a49740926c2c450a1505a4a0f8954a <b13abcb7ddd8d38de769486db5bd917537b32ab1

Published CVSS scores

5.5CISA-ADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5NIST NVDCVSS: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

CWE-476NULL Pointer Dereference
T1499.004Application or System Exploitation

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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