[CVE-2026-53287][MODERATE REGULAR] audit: fix incorrect inheritable capability in CAPSET records

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

CVE: CVE-2026-53287
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: audit: fix incorrect inheritable capability in CAPSET records
Commit: 75bd76c9eb2de9afeca03dc5152ebca5fb8fc816
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=75bd76c9eb2de9afeca03dc5152ebca5fb8fc816
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53287
Analysis date: Fri, 26 Jun 2026 16:26:38 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline manual review recommended / Actionable Moderate candidate
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-53287 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53287

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 REGULAR
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
======================================================================

CVE-2026-53287	MODERATE	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N';CWE-778;CWE-682;CWE-840;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N';BEST CVSS score: '5.5';DESCR 'AUDIT_CAPSET records can report the process inheritable capability set incorrectly because __audit_log_capset copies cap_effective into the inheritable field instead of cap_inheritable. This corrupts audit evidence for successful capset operations and can hide changes to inheritable capabilities that may be relevant before a later privilege changing exec. For the CVSS the PR:L is used because a local process must be able to perform a successful capset operation or run in a capability bearing context, but full administrative control is not necessarily required in container or service account deployments. The issue is not network reachable and does not provide a direct kernel memory corruption primitive. Impact is audit integrity loss, with no direct confidentiality or availability impact.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended / Actionable Moderate candidate (with actual score 4)  SKIP CVE-2026-53287  SKIP The Fixes patch not applied yet, so unlikely that actual: e68b75a027bb94066576139ee33676264f867b87 YES  NO NO unknown 	MAYBE	SIMPLEFIX LINUS 	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=4
ActionableScoreLower=3

1. **ActionableScore**
* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline manual review recommended / Actionable Moderate candidate**::

2. **Signal breakdown**
* Local trigger: +1. A local process must perform a successful capset operation or run in a capability-bearing context.
* Integrity impact plausible: +1. The bug corrupts AUDIT_CAPSET records by logging cap_effective instead of cap_inheritable.
* Broad security-relevant subsystem: +1. Linux audit records are commonly used for compliance, incident response, and forensic review.
* Paranoid additional signal: +1. The commit explicitly notes that inheritable capability changes used before a privilege-changing exec may be masked in the audit trail.
* Not counted: no memory corruption, no UAF, no OOB access, no kernel crash, no direct privilege escalation primitive, and no network reachability.

3. **Reachability analysis**
The bug is local and depends on successful capset activity. A fully unprivileged user may have limited ability to create meaningful capability transitions, but container root, service accounts, or reduced-capability processes can make this relevant without full host-root control. Namespaces and containerized deployments matter because capability-bearing but restricted processes are common there. The affected path is in the audit subsystem and only has security impact where audit records are collected and relied on.

4. **Severity interpretation**
This behaves more like an actionable Moderate than an Important-class kernel vulnerability. The realistic impact is audit integrity loss and forensic evasion, not kernel compromise. Theoretical privilege escalation is not caused by this bug itself, but the bug can hide capability changes that may be relevant to a later privilege-changing exec. Because this affects security audit evidence, it should not be treated as a trivial cleanup.

5. **One-sentence report phrase**
AUDIT_CAPSET records incorrectly logged cap_effective as cap_inheritable, allowing local capability changes to be misrepresented in audit logs and potentially masking security-relevant pre-exec capability preparation.

6. **Manual review recommendation**
MANUAL CHECK RECOMMENDED.
Manual review is recommended because the issue affects audit integrity and compliance evidence, even though it is not memory corruption and does not directly enable privilege escalation.

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

Patch: audit: fix incorrect inheritable capability in CAPSET records
Commit: 75bd76c9eb2de9afeca03dc5152ebca5fb8fc816
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=75bd76c9eb2de9afeca03dc5152ebca5fb8fc816

Commit description:

__audit_log_capset() records the effective capability set into the
inheritable field due to a copy-paste error. Every CAPSET audit
record therefore reports cap_pi (process inheritable) with the value
of cap_effective instead of cap_inheritable.

This silently corrupts audit data used for compliance and forensic
analysis: an attacker who modifies inheritable capabilities to
prepare for a privilege-escalating exec would have the change masked
in the audit trail.

The bug has been present since the original introduction of CAPSET
audit records in 2008.

Cc: stable@vger.kernel.org
Fixes: e68b75a ("When the capset syscall is used it is not possible for audit to record the actual capbilities being added/removed.  This patch adds a new record type which emits the target pid and the eff, inh, and perm cap sets.")
Reviewed-by: Ricardo Robaina <rrobaina@redhat.com>
Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Sergio Correia <scorreia@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  kernel/auditsc.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=75bd76c9eb2de9afeca03dc5152ebca5fb8fc816

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

The original Linux kernel CVE announcement for CVE-2026-53287 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53287

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:L/UI:N/S:U/C:N/I:L/A:N
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
  The Best / paranoid CVSS score: 5.5

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: 3
  Paranoid ActionableScore: 4

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: NO
Published priority for this report (same as in Subject): MODERATE REGULAR

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).