[CVE-2026-80757][MODERATE 7.0] selinux: reject a class permission count below its inherited common

[CVE-2026-80757][MODERATE 7.0] selinux: reject a class permission count below its inherited common

[AL-KERNEL]

CVE: CVE-2026-80757
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: selinux: reject a class permission count below its inherited common
Commit: 2002ff745db64ac83ee1bb9ff78196d2d68bfdb3
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2002ff745db64ac83ee1bb9ff78196d2d68bfdb3
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80757
Analysis date: Thu, 03 Sep 2026 05:14:57 -0400
ActionableScore: 8
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A malformed SELinux policy can declare a class permission count smaller than its inherited common permission count, causing security_get_permissions() to write past a class sized heap array during policy loading and creating a local kernel memory corruption risk.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-80757 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80757

The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.

The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.

Published priority for this report: MODERATE 7.0
Manual review required: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-80757	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80757 CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-787;CWE-122;*CWE-20;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H';BEST CVSS score: '7.8';DESCR 'A malformed SELinux policy can define a class that inherits a common permission set while declaring fewer permissions than that common. During policy loading, security_get_permissions() can then map common permissions into an array sized by the smaller class permission count, causing an out of bounds heap write in kernel memory. For the CVSS the PR:L is used for the paranoid score because some deployments may delegate SELinux policy loading to a confined policy management process or reduced capability administrator, although typical systems require high privileges to load SELinux policy. The issue is not network reachable and requires local ability to supply or load a policy image. Impact is at least local denial of service via kernel memory corruption and in worst case may allow confidentiality, integrity, and availability impact due to the OOB heap write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)	YES	WRITE OOB SIMPLEFIX IMPROVEONLY LINUS KPANIC  DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=8
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 8
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Memory corruption, Strong corruption primitive: +2. The commit explicitly states an out of bounds heap write during SELinux policy load.
* Weak LPE concern: +1. Kernel heap corruption can theoretically affect security sensitive state, but the patch does not show controlled target selection, reclaim, or an arbitrary write primitive.
* Reliable kernel crash / strong DoS: +1. An OOB heap write during policy parsing can realistically crash or corrupt the kernel.
* Integrity impact plausible: +1. The corrupted object is in SELinux policy/security state or adjacent heap memory.
* Broad/security sensitive subsystem: +1. SELinux policydb is a core LSM policy subsystem on many enterprise systems.
* Requires admin/root/CAP in typical deployments: -2. Loading SELinux policy normally requires highly privileged local access.

Paranoid additions / changes:

* Privilege escalation plausible: +2 instead of weak +1. A malformed policy image provides attacker influenced parser input and reaches a kernel heap OOB write in a security critical subsystem.
* Confidentiality impact plausible: +1. Kernel heap corruption can plausibly affect sensitive kernel or LSM state.
* No full admin penalty in the paranoid model. Some environments may delegate policy loading to a reduced capability policy management process or service account, so this is not always equivalent to full host root.

## 3. Reachability analysis

The bug is local and requires the ability to supply and load a malformed SELinux policy image. It is not network reachable by itself. In typical deployments, SELinux policy loading is restricted to root or a highly privileged policy management path, so the conservative interpretation applies an admin privilege penalty. Namespaces and containers usually do not make SELinux policy loading available to ordinary container users, but delegated policy management or reduced capability service accounts can make PR:L a defensible paranoid interpretation.

The vulnerable path is not a packet parser or default remote interface. However, SELinux is a broadly deployed security subsystem, and the bug is in policy parsing for a privileged kernel security object. Realistic exploitation depends on whether an attacker can influence a policy image accepted by the system.

## 4. Severity interpretation

This is not an ordinary Moderate validation bug. The patch prevents a concrete out of bounds heap write, not just a warning or malformed metadata rejection. Realistic exploitation for LPE is not demonstrated because there is no shown arbitrary write target, heap shaping, or reclaim primitive. Still, kernel heap corruption in SELinux policy loading is sufficiently serious to require manual review and should be treated as at least Actionable Moderate, with a Strong Important candidate paranoid bucket.

## 5. One-sentence report phrase

A malformed SELinux policy can declare a class permission count smaller than its inherited common permission count, causing security_get_permissions() to write past a class sized heap array during policy loading and creating a local kernel memory corruption risk.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK.

Reason: the patch fixes an explicitly described OOB heap write in kernel memory inside SELinux policy parsing, with plausible DoS and potential privilege escalation concerns despite privileged reachability in typical deployments.

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UPSTREAM PATCH SUMMARY
======================================================================

Patch: selinux: reject a class permission count below its inherited common
Commit: 2002ff745db64ac83ee1bb9ff78196d2d68bfdb3
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2002ff745db64ac83ee1bb9ff78196d2d68bfdb3

Commit description:

security_get_permissions() maps an inherited common's permissions into
an array sized by the class's own permissions.nprim, but class_read()
takes that nprim verbatim from the policy image and never checks that it
covers the common.  A class that inherits a common of N permissions while
declaring a smaller nprim is accepted, and on load the common's
permissions are written past the class-sized array -- an out-of-bounds
heap write.

Reject a class whose permission count is below its inherited common's.
Well-formed policies, where the class count already includes the
inherited permissions, are unaffected.

Cc: stable@vger.kernel.org
Fixes: 55fcf09 ("selinux: add support for querying object classes and permissions from the running policy")
Signed-off-by: Bryam Vargas <hexlabsecurity@proton.me>
Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  security/selinux/ss/policydb.c

Diff excerpt:

Not included in this email. See the upstream URL for the full patch.

Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2002ff745db64ac83ee1bb9ff78196d2d68bfdb3

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DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-80757 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80757

The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.

The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.

The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.

Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:

  Conservative CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.8

The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.

CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.

A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.

  Conservative ActionableScore: 5
  Paranoid ActionableScore: 8

The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.

For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:

  ActionableScore below 5   -> MODERATE REGULAR
  ActionableScore 5 or more -> MODERATE 7.0

The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.

There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).

KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.

AL-KERNEL base severity for this report: MODERATE
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): MODERATE 7.0

These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).

Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).