[CVE-2026-80756][LOW] selinux: do not cancel a policy conversion that never started

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-80756
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: selinux: do not cancel a policy conversion that never started
Commit: 2d29983104f06f5b0babcd5a25a0f0408272cd27
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2d29983104f06f5b0babcd5a25a0f0408272cd27
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80756
Analysis date: Thu, 03 Sep 2026 05:21:35 -0400
ActionableScore: 2
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A NULL pointer dereference in the SELinux first policy load error path can allow a privileged local actor able to write to `/sys/fs/selinux/load` to crash the kernel if policy node creation fails.

======================================================================
ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-80756 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80756

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: LOW
Manual review required: NO

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

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-80756	LOW	https://www.kernelcve.org/list/?q=CVE-2026-80756 CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';**CWE-476;CWE-703;CWE-754;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'A NULL pointer dereference in the SELinux policy load error path can occur when the first policy load fails while creating selinuxfs policy nodes. In this first load case there is no outgoing policy and state policy is still NULL, but selinux_policy_cancel can still try to cancel sidtab conversion through the old policy pointer. A local actor who can write to /sys/fs/selinux/load and trigger a failing policy load can cause a kernel crash. For the CVSS the PR:L is used for the paranoid score because some deployments may delegate SELinux policy loading to a local service or reduced administrative role. In default systems direct triggering usually requires high privileges. The issue is not network reachable. Impact is denial of service only via NULL pointer dereference with no supported confidentiality or integrity impact.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)	YES	DANGER NULLPTR DISK SIMPLEFIX LINUS  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	NO	NO	checked

======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=2
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Conservative signals:

* Reliable kernel crash / strong DoS: +1. The patch describes a concrete NULL pointer dereference in `selinux_policy_cancel()` when `oldpolicy` is NULL.
* Requires admin/root/CAP_* in typical deployments: -2. Writing to `/sys/fs/selinux/load` and loading SELinux policy is normally restricted to highly privileged policy management paths.
* Rare or difficult triggering condition: -1. The bug requires a first policy load plus failure while building the selinuxfs policy tree.
* Weak corruption only: +0. This is a NULL pointer dereference, not UAF, OOB write, double free, type confusion, refcount abuse, or attacker controlled memory corruption.

Paranoid signals:

* Reliable kernel crash / strong DoS: +1. A successful trigger can crash the kernel.
* Broad security subsystem exposure: +1. SELinux is a common LSM in many enterprise deployments, although the affected policy load path is privileged and not commonly exposed.
* Reduced privilege deployment concern: 0. Some systems may delegate policy loading to a confined service or reduced administrative role, so the full -2 root penalty may be too harsh in a paranoid interpretation.
* No LPE or memory corruption bonus. The patch supports NULL dereference only and does not show stale object reuse, writable freed memory, arbitrary write, info leak, or privilege escalation.

## 3. Reachability analysis

The bug is triggered locally through a write to `/sys/fs/selinux/load`. In normal deployments this requires administrative SELinux policy loading privileges, usually root or an equivalent privileged policy management context. It is not network reachable. Namespaces and containers generally do not make this reachable unless a container or service is explicitly delegated SELinux policy loading on the host, which is unusual. Realistic exploitation is a privileged or delegated local DoS during a failing first policy load.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like kernel DoS issue, not an Important-class vulnerability. The failure mode is a NULL pointer dereference with high privilege requirements and special first-load error-path conditions. Theoretical impact is kernel crash only. There is no supported evidence of UAF, reclaim control, object replacement, arbitrary write, confidentiality impact, integrity impact, or practical privilege escalation.

## 5. One-sentence report phrase

A NULL pointer dereference in the SELinux first policy load error path can allow a privileged local actor able to write to `/sys/fs/selinux/load` to crash the kernel if policy node creation fails.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can be auto-closed for urgent triage purposes because the bug is privileged, local only, special-condition dependent, and supported impact is DoS only via NULL pointer dereference.

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

Patch: selinux: do not cancel a policy conversion that never started
Commit: 2d29983104f06f5b0babcd5a25a0f0408272cd27
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2d29983104f06f5b0babcd5a25a0f0408272cd27

Commit description:

sel_write_load() calls selinux_policy_cancel() when sel_make_policy_nodes()
fails, and that helper dereferences the outgoing policy to cancel its
sidtab conversion. On the first policy load there is no outgoing policy:
security_load_policy() returns early for that case, before it converts
anything, and state->policy is still NULL. A first load that fails while
building the selinuxfs tree therefore takes a NULL dereference in
selinux_policy_cancel(), reached from a write(2) to /sys/fs/selinux/load.

Skip the cancel when there is no old policy, mirroring the check
security_load_policy() already makes before it converts.

Cc: stable@vger.kernel.org
Fixes: 02a52c5 ("selinux: move policy commit after updating selinuxfs")
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/services.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=2d29983104f06f5b0babcd5a25a0f0408272cd27

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

The original Linux kernel CVE announcement for CVE-2026-80756 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80756

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:H/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 0
  Paranoid ActionableScore: 2

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).