CVE-2025-21637

Kernel crash via SCTP sysctl null dereference

Published Jan 19, 2025 · Updated Aug 5, 2026

NULL pointer dereference in the SCTP udp_port sysctl in affected Linux kernel releases allows local users to crash the kernel. The handler derives its network namespace from current->nsproxy even though that pointer can be NULL while the calling task exits, so dereferencing it produces a kernel Oops. Triggering the flaw requires local low-privileged execution and concurrent access to the SCTP udp_port sysctl during task exit; the bounded impact is service interruption.

CVSS severity5.5
Medium
EPSS probability0.21%
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 SCTP udp_port sysctl in affected Linux kernel releases allows local users to crash the kernel. The handler derives its network namespace from current->nsproxy even though that pointer can be NULL while the calling task exits, so dereferencing it produces a kernel Oops. Triggering the flaw requires local low-privileged execution and concurrent access to the SCTP udp_port sysctl during task exit; the bounded impact is service interruption.

The record

CVE
CVE-2025-21637
Published
Jan 19, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-476, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 19, 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=046c052b475e7119b6a30e3483e2888fc606a2f8 <0a0966312ac3eedd7f5f2a766ed4702df39a9a65
  2. Affected versionversion=046c052b475e7119b6a30e3483e2888fc606a2f8 <55627918febdf9d71107a1e68d1528dc591c9a15
  3. Affected versionversion=046c052b475e7119b6a30e3483e2888fc606a2f8 <5b77d73f3be5102720fb685b9e6900e3500e1096
  4. Affected versionversion=046c052b475e7119b6a30e3483e2888fc606a2f8 <c10377bbc1972d858eaf0ab366a311b39f8ef1b6
  5. Affected versionversion=046c052b475e7119b6a30e3483e2888fc606a2f8 <e919197fb8616331f5dc81e4c3cc3d12769cb725
  6. Affected versionversion=5.11

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=046c052b475e7119b6a30e3483e2888fc606a2f8 <0a0966312ac3eedd7f5f2a766ed4702df39a9a65; version=046c052b475e7119b6a30e3483e2888fc606a2f8 <55627918febdf9d71107a1e68d1528dc591c9a15; version=046c052b475e7119b6a30e3483e2888fc606a2f8 <5b77d73f3be5102720fb685b9e6900e3500e1096; version=046c052b475e7119b6a30e3483e2888fc606a2f8 <c10377bbc1972d858eaf0ab366a311b39f8ef1b6; version=046c052b475e7119b6a30e3483e2888fc606a2f8 <e919197fb8616331f5dc81e4c3cc3d12769cb725; version=5.11

Published CVSS scores

5.5Canonical UbuntuCVSS: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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