CVE-2026-23409

System crash via cyclic AppArmor policy chains

Published Apr 1, 2026 · Updated Apr 1, 2026

Infinite-loop handling in affected Linux Kernel releases allows local users to crash the system by loading a crafted AppArmor policy. The differential-encoding verifier in security/apparmor/match.c confuses verified states with states in the current chain and compares inner iterators instead of the outer-loop iterator, so a cyclic chain passes validation. Exploitation requires the ability to load arbitrary AppArmor profiles, obtained through a cooperating privileged application or an attacker-controlled container.

CVSS severity5.5
Medium
EPSS probability0.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Infinite-loop handling in affected Linux Kernel releases allows local users to crash the system by loading a crafted AppArmor policy. The differential-encoding verifier in security/apparmor/match.c confuses verified states with states in the current chain and compares inner iterators instead of the outer-loop iterator, so a cyclic chain passes validation. Exploitation requires the ability to load arbitrary AppArmor profiles, obtained through a cooperating privileged application or an attacker-controlled container.

The record

CVE
CVE-2026-23409
Published
Apr 1, 2026
Updated
Apr 1, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-835, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 1, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 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=031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 <1ff4857fac56ac5a90ee63b24db05fa5e91a45aa
  2. Affected versionversion=031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 <34fc60b125ed1d4eb002c76b0664bf0619492167
  3. Affected versionversion=031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 <39440b137546a3aa383cfdabc605fb73811b6093
  4. Affected versionversion=031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 <623a9d211bbbb031bb1cbdb38b23487648167f8a
  5. Affected versionversion=031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 <f90e3ecd9e1ed69f1a370f866ceed1f104f3ab4a
  6. Affected versionversion=4.17

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 <1ff4857fac56ac5a90ee63b24db05fa5e91a45aa; version=031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 <34fc60b125ed1d4eb002c76b0664bf0619492167; version=031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 <39440b137546a3aa383cfdabc605fb73811b6093; version=031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 <623a9d211bbbb031bb1cbdb38b23487648167f8a; version=031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 <f90e3ecd9e1ed69f1a370f866ceed1f104f3ab4a; version=4.17

Published CVSS scores

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.

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

CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
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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