CVE-2025-21903

Local kernel crash via NULL address dereference

Published Apr 1, 2025 · Updated May 11, 2026

NULL pointer dereference in Linux kernel 6.7 through 6.12.18 and 6.13 through 6.13.6 allows local users to crash the host via MCTP-over-I3C. The mctp_i3c_header_create function passes unchecked destination or source address pointers to memcpy while constructing an internal header. A missing neighbor entry or a packet from another protocol supplies the NULL address; exploitation requires local low-privileged access and can halt the host.

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 Linux kernel 6.7 through 6.12.18 and 6.13 through 6.13.6 allows local users to crash the host via MCTP-over-I3C. The mctp_i3c_header_create function passes unchecked destination or source address pointers to memcpy while constructing an internal header. A missing neighbor entry or a packet from another protocol supplies the NULL address; exploitation requires local low-privileged access and can halt the host.

The record

CVE
CVE-2025-21903
Published
Apr 1, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
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

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=6.7
  2. Affected versionversion=c8755b29b58ec65be17bcb8c40763d2dcb1f1db5 <740bf9c9b715cc327d34b1e2d4ee79fcd4c47a56
  3. Affected versionversion=c8755b29b58ec65be17bcb8c40763d2dcb1f1db5 <cf7ee25e70c6edfac4553d6b671e8b19db1d9573
  4. Affected versionversion=c8755b29b58ec65be17bcb8c40763d2dcb1f1db5 <d8be54c35aee29d96d1350b1b6f153be4da37c07

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.7; version=c8755b29b58ec65be17bcb8c40763d2dcb1f1db5 <740bf9c9b715cc327d34b1e2d4ee79fcd4c47a56; version=c8755b29b58ec65be17bcb8c40763d2dcb1f1db5 <cf7ee25e70c6edfac4553d6b671e8b19db1d9573; version=c8755b29b58ec65be17bcb8c40763d2dcb1f1db5 <d8be54c35aee29d96d1350b1b6f153be4da37c07

Published CVSS scores

6.8SUSECVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
5.5SUSECVSS: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.

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

T1499.004Application or System Exploitation

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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