CVE-2026-23409· NVD / CVE Program· CNA Linux

apparmor: fix differential encoding verification

Noroxi assessment

Priority: Monitor (action score 22/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.17% (FIRST EPSS).
Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
Fixed version: Linux Linux 0fab44285445e9012674396d5c1236a67da518e0, 1439150cd3c411228b387ab5efca92199d2a659a, 1ff4857fac56ac5a90ee63b24db05fa5e91a45aa; azl3 kernel 6.6.0.0-1 on Azure Linux 3.0 6.6.130.1-1.

Low priority for now. Upgrade to Linux Linux 0fab44285445e9012674396d5c1236a67da518e0, 1439150cd3c411228b387ab5efca92199d2a659a, 1ff4857fac56ac5a90ee63b24db05fa5e91a45aa; azl3 kernel 6.6.0.0-1 on Azure Linux 3.0 6.6.130.1-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: apparmor: fix differential encoding verification Differential encoding allows loops to be created if it is abused. To prevent this the unpack should verify that a diff-encode chain terminates. Unfortunately the differential encode verification had two bugs. 1. it conflated states that had gone through check and already been marked, with states that were currently being checked and marked. This means that loops in the current chain being verified are treated as a chain that has already been verified. 2. the order bailout on already checked states compared current chain check iterators j,k instead of using the outer loop iterator i. Meaning a step backwards in states in the current chain verification was being mistaken for moving to an already verified state. Move to a double mark scheme where already verified states get a different mark, than the current chain being kept. This enables us to also drop the backwards verification check that was the cause of the second error as any already verified state is already marked.

MediumCVSS 5.5 · v3.1—No exploit Fix available

Denial of service

Published: Apr 1, 2026
Updated: Jun 17, 2026
EPSS: 0.1% · 6th percentile
CWE: CWE-835

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 22 / 40 · 5.5 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.1%

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
linux	linux kernel	cpe:2.3:o:linux:linux_kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

linux linux kernel4.17.1 and later · before 5.10.253
linux linux kernel5.11 and later · before 5.15.203
linux linux kernel5.16 and later · before 6.1.169
linux linux kernel6.2 and later · before 6.6.130
linux linux kernel6.7 and later · before 6.12.77
linux linux kernel6.13 and later · before 6.18.18
linux linux kernel6.19 and later · before 6.19.8
linux linux kernel4.17
linux linux kernel7.0

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

Linux Linux
- 4.17affected
- 031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 and later · before ff7c73744fafe944ed9a7b2b7cf6c8d5557a3d84affected · git
- 031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 and later · before 1439150cd3c411228b387ab5efca92199d2a659aaffected · git
- 031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 and later · before 0fab44285445e9012674396d5c1236a67da518e0affected · git
- 031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 and later · before f90e3ecd9e1ed69f1a370f866ceed1f104f3ab4aaffected · git
- 031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 and later · before 34fc60b125ed1d4eb002c76b0664bf0619492167affected · git
- 031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 and later · before 623a9d211bbbb031bb1cbdb38b23487648167f8aaffected · git
- 031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 and later · before 1ff4857fac56ac5a90ee63b24db05fa5e91a45aaaffected · git
- 031dcc8f4e84fea37dc6f78fdc7288aa7f8386c3 and later · before 39440b137546a3aa383cfdabc605fb73811b6093affected · git
- before 4.17not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Debian:12	linux	before 6.1.164-1	6.1.164-1
Debian:13	linux	before 6.12.74-2	6.12.74-2
Debian:14	linux	before 6.19.6-2	6.19.6-2
SUSE:Linux Enterprise Live Patching 15 SP6	kernel-default	before 6.4.0-150600.23.112.1	6.4.0-150600.23.112.1
SUSE:Linux Enterprise Live Patching 15 SP6	kernel-livepatch-SLE15-SP6_Update_26	before 1-150600.13.3.1	1-150600.13.3.1
SUSE:Linux Enterprise Server 15 SP6-LTSS	kernel-64kb	before 6.4.0-150600.23.112.1	6.4.0-150600.23.112.1
SUSE:Linux Enterprise Server 15 SP6-LTSS	kernel-default-base	before 6.4.0-150600.23.112.1.150600.12.52.1	6.4.0-150600.23.112.1.150600.12.52.1
SUSE:Linux Enterprise Server 15 SP6-LTSS	kernel-docs	before 6.4.0-150600.23.112.1	6.4.0-150600.23.112.1
SUSE:Linux Enterprise Server 15 SP6-LTSS	kernel-obs-build	before 6.4.0-150600.23.112.1	6.4.0-150600.23.112.1
SUSE:Linux Enterprise Server 15 SP6-LTSS	kernel-source	before 6.4.0-150600.23.112.1	6.4.0-150600.23.112.1
SUSE:Linux Enterprise Server 15 SP6-LTSS	kernel-syms	before 6.4.0-150600.23.112.1	6.4.0-150600.23.112.1
SUSE:Linux Enterprise Server 15 SP6-LTSS	kernel-zfcpdump	before 6.4.0-150600.23.112.1	6.4.0-150600.23.112.1

Same product

linux: all records

Other highest-scoring records for the same primary product.

CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
89Now
CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
85Now
CVE-2016-5195Race condition in mm/gup.c in the Linux kernel 2.x through 4.x before 4.8.3 allows local users to gain privileges by leveraging incorrect haKEV
83Now

Published before and after this one in the same product

← EarlierCVE-2026-23407Apr 1, 2026 · apparmor: fix missing bounds check on DEFAULT table in verify_dfa()
31Monitor
← EarlierCVE-2026-23408Apr 1, 2026 · apparmor: Fix double free of ns_name in aa_replace_profiles()
31Monitor
Later →CVE-2026-23410Apr 1, 2026 · apparmor: fix race on rawdata dereference
31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
Linux Linux	0fab44285445e9012674396d5c1236a67da518e0	Vendor (CNA)
Linux Linux	1439150cd3c411228b387ab5efca92199d2a659a	Vendor (CNA)
Linux Linux	1ff4857fac56ac5a90ee63b24db05fa5e91a45aa	Vendor (CNA)
Linux Linux	34fc60b125ed1d4eb002c76b0664bf0619492167	Vendor (CNA)
Linux Linux	39440b137546a3aa383cfdabc605fb73811b6093	Vendor (CNA)
Linux Linux	623a9d211bbbb031bb1cbdb38b23487648167f8a	Vendor (CNA)
Linux Linux	f90e3ecd9e1ed69f1a370f866ceed1f104f3ab4a	Vendor (CNA)
Linux Linux	ff7c73744fafe944ed9a7b2b7cf6c8d5557a3d84	Vendor (CNA)
azl3 kernel 6.6.0.0-1 on Azure Linux 3.0	6.6.130.1-1 · CBL-Mariner Releases	Microsoft (MSRC)
debian:linux	6.1.164-1 · Debian:12	Package registry (OSV)
suse:kernel-64kb	6.4.0-150600.23.112.1 · SUSE:Linux Enterprise Server 15 SP6-LTSS	Package registry (OSV)
suse:kernel-default	6.4.0-150600.23.112.1 · SUSE:Linux Enterprise Live Patching 15 SP6	Package registry (OSV)
suse:kernel-default-base	6.4.0-150600.23.112.1.150600.12.52.1 · SUSE:Linux Enterprise Server 15 SP6-LTSS	Package registry (OSV)
suse:kernel-docs	6.4.0-150600.23.112.1 · SUSE:Linux Enterprise Server 15 SP6-LTSS	Package registry (OSV)
suse:kernel-livepatch-SLE15-SP6_Update_26	1-150600.13.3.1 · SUSE:Linux Enterprise Live Patching 15 SP6	Package registry (OSV)
suse:kernel-obs-build	6.4.0-150600.23.112.1 · SUSE:Linux Enterprise Server 15 SP6-LTSS	Package registry (OSV)
suse:kernel-source	6.4.0-150600.23.112.1 · SUSE:Linux Enterprise Server 15 SP6-LTSS	Package registry (OSV)
suse:kernel-syms	6.4.0-150600.23.112.1 · SUSE:Linux Enterprise Server 15 SP6-LTSS	Package registry (OSV)
suse:kernel-zfcpdump	6.4.0-150600.23.112.1 · SUSE:Linux Enterprise Server 15 SP6-LTSS	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

CVE-2026-3144821 days apartext4: avoid infinite loops caused by residual data
37Monitor
CVE-2026-5293384 days apartio_uring/poll: fix signed comparison in io_poll_get_ownership()
31Monitor
CVE-2026-234512 days apartbonding: prevent potential infinite loop in bond_header_parse()
30Monitor
CVE-2026-3155223 days apartwifi: wlcore: Return -ENOMEM instead of -EAGAIN if there is not enough headroom
30Monitor
CVE-2026-4605256 days apartceph: only d_add() negative dentries when they are unhashed
30Monitor
CVE-2026-64148109 days apartpds_core: fix error handling in pdsc_devcmd_wait
30Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Someone with local access to the system can trigger it.
A low-privileged account is enough.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: none
Integrity: none
Availability: high · the service can be disrupted

Attack vector: Local
Attack complexity: Low
Privileges required: Low
User interaction: None
Scope: Unchanged
Confidentiality impact: None
Integrity impact: None
Availability impact: High

Weakness class (CWE)

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

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

Fix✗ → ✓Sep 28, 2026, 10:10 PM UTC

For records you follow, these changes also arrive as notifications. →

References

git.kernel.org/stable/c/0fab44285445e9012674396d5c1236a67da518e0

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records