CVE-2026-53349

Kernel crash via stale netfilter callback

Published Jul 1, 2026 · Updated Jul 1, 2026

Use-after-free in the Linux Kernel netfilter subsystem allows local users to crash the kernel through a stale expectation callback. The nf_ct_helper_expectfn_unregister() path removes only the callback descriptor, leaving live expectations with exp->expectfn pointers into unloaded NAT-helper module text that init_conntrack() later invokes. Triggering the crash requires CAP_SYS_MODULE in the initial user namespace, a live expectation, helper-module removal, and a connection matching that expectation.

CVSS severity5.5
Medium
EPSS probability0.16%
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 the Linux Kernel netfilter subsystem allows local users to crash the kernel through a stale expectation callback. The nf_ct_helper_expectfn_unregister() path removes only the callback descriptor, leaving live expectations with exp->expectfn pointers into unloaded NAT-helper module text that init_conntrack() later invokes. Triggering the crash requires CAP_SYS_MODULE in the initial user namespace, a live expectation, helper-module removal, and a connection matching that expectation.

The record

CVE
CVE-2026-53349
Published
Jul 1, 2026
Updated
Jul 1, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1499.004
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Jul 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 1, 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=2.6.20
  2. Affected versionversion=f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4 <29d8cc44bbdf7b83a1929912214afe6643c1b4f1
  3. Affected versionversion=f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4 <9d017671dcfcec23321fb7962dea624f9e71ddb1
  4. Affected versionversion=f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4 <bf8c0b5dd203be94c2ad50e264cec19267c6bd39
  5. Affected versionversion=f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4 <c3009418f9fa1dcb3eb86f4d8c92583537b5faa3
  6. Affected versionversion=f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4 <f92c90a2a3e6ff6f9f7fe88fde9004b4ca8f956d
  7. Affected versionversion=f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4 <fbfde85308b99938a6092c48753214d190ece48d

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

The Linux Kernel Organization · Linux Kernelversion=2.6.20; version=f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4 <29d8cc44bbdf7b83a1929912214afe6643c1b4f1; version=f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4 <9d017671dcfcec23321fb7962dea624f9e71ddb1; version=f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4 <bf8c0b5dd203be94c2ad50e264cec19267c6bd39; version=f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4 <c3009418f9fa1dcb3eb86f4d8c92583537b5faa3; version=f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4 <f92c90a2a3e6ff6f9f7fe88fde9004b4ca8f956d; version=f587de0e2feb9eb9b94f98d0a7b7437e4d6617b4 <fbfde85308b99938a6092c48753214d190ece48d

Published CVSS scores

5.5CanonicalCVSS: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

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
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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