CVE-2025-21945Network attack vector

Kernel memory corruption via stale SMB lock

Published Apr 1, 2025 · Updated Aug 5, 2026

Use-after-free in affected Linux kernel ksmbd releases allows remote authenticated users to corrupt memory via a crafted SMB2 LOCK request. A zero-length lock remains linked while smb2_lock reuses stale file-lock state, leaving freed objects reachable during error handling. A low-privileged account with an open file on an exported share is sufficient; exploitation can disclose or corrupt kernel memory and panic the server.

CVSS severity8.8
High
EPSS probability0.51%
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 affected Linux kernel ksmbd releases allows remote authenticated users to corrupt memory via a crafted SMB2 LOCK request. A zero-length lock remains linked while smb2_lock reuses stale file-lock state, leaving freed objects reachable during error handling. A low-privileged account with an open file on an exported share is sufficient; exploitation can disclose or corrupt kernel memory and panic the server.

The record

CVE
CVE-2025-21945
Published
Apr 1, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416, T1190
Attack vector
network
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=0626e6641f6b467447c81dd7678a69c66f7746cf <410ce35a2ed6d0e114132bba29af49b69880c8c7
  2. Affected versionversion=0626e6641f6b467447c81dd7678a69c66f7746cf <636e021646cf9b52ddfea7c809b018e91f2188cb
  3. Affected versionversion=0626e6641f6b467447c81dd7678a69c66f7746cf <84d2d1641b71dec326e8736a749b7ee76a9599fc
  4. Affected versionversion=0626e6641f6b467447c81dd7678a69c66f7746cf <8573571060ca466cbef2c6f03306b2cc7b883506
  5. Affected versionversion=0626e6641f6b467447c81dd7678a69c66f7746cf <a0609097fd10d618aed4864038393dd75131289e
  6. Affected versionversion=5.15

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=0626e6641f6b467447c81dd7678a69c66f7746cf <410ce35a2ed6d0e114132bba29af49b69880c8c7; version=0626e6641f6b467447c81dd7678a69c66f7746cf <636e021646cf9b52ddfea7c809b018e91f2188cb; version=0626e6641f6b467447c81dd7678a69c66f7746cf <84d2d1641b71dec326e8736a749b7ee76a9599fc; version=0626e6641f6b467447c81dd7678a69c66f7746cf <8573571060ca466cbef2c6f03306b2cc7b883506; version=0626e6641f6b467447c81dd7678a69c66f7746cf <a0609097fd10d618aed4864038393dd75131289e; version=5.15

Published CVSS scores

7.8CISA ADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
8.8LinuxCVSS:3.1/AV:N/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)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
T1190Exploit Public-Facing Application

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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