[CVE-2026-53361][MODERATE 7.0] af_unix: Set gc_in_progress to true in unix_gc(). [ Upstream

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

CVE: CVE-2026-53361
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: af_unix: Set gc_in_progress to true in unix_gc(). [ Upstream
Commit: 82c17e13d404f686e164590483fd6c1abaa675d0
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=82c17e13d404f686e164590483fd6c1abaa675d0
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53361
Analysis date: Sat, 04 Jul 2026 08:56:52 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A local unprivileged user may race AF_UNIX GC scheduling with MSG_PEEK so unix_gc runs while gc_in_progress is false, confusing GC lifetime handling and creating at least a local DoS risk with weak UAF concern.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-53361 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53361

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-2026-53361	MODERATE	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-362;*CWE-416;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A race in AF_UNIX garbage collection can allow unix_gc to run while gc_in_progress is false. MSG_PEEK handling in unix_peek_fpl relies on this flag to avoid confusing garbage collection of file descriptor references passed over UNIX sockets. A local user can potentially trigger the race with AF_UNIX socket activity and MSG_PEEK while GC work is scheduled. For the CVSS the PR:L is used because a local process is required, but no administrative privileges are needed to use ordinary AF_UNIX sockets. The base impact is local denial of service through GC corruption or kernel crash. The paranoid impact treats this as a possible use-after-free candidate because the bug affects GC and object lifetime tracking, so confidentiality and integrity impact may be possible and the issue should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)  SKIP CVE-2026-53361  SKIP The Fixes patch not applied yet, so unlikely that actual: 8b90a9f819dc2a06baae4ec1a64d875e53b824ec YES  NO NO unknown 	MAYBE	REMOTE DANGER HARDWARE KPANIC 	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. Ordinary AF_UNIX sockets and MSG_PEEK are available to local unprivileged processes.
* Memory corruption, weak or indirect corruption candidate: +1. The patch concerns GC confusion and object lifetime state, but does not show controlled reclaim, overwrite, callback dispatch, or type confusion.
* Real lifetime corruption: +1. The bug affects AF_UNIX garbage collection state and file reference handling around unix_peek_fpl and MSG_PEEK.
* Availability impact realistic: +1. Confused AF_UNIX GC can plausibly lead to leaked references, stuck cleanup, or kernel failure conditions.
* Broad default subsystem: +1. AF_UNIX is a default and widely used local IPC subsystem.
* Hard or unreliable race: -1. The described failure requires a timing window between concurrent unix_schedule_gc and unix_gc execution.

Conservative total: 4.

Paranoid adjustment:

* The paranoid score does not subtract the race penalty because repeated local AF_UNIX socket activity can make the race more naturally triggerable under load.
* Paranoid total: 5.

Not counted:

* No remote reachable signal. This is local AF_UNIX IPC, not network-triggered.
* No strong LPE plausibility. The patch does not demonstrate attacker-controlled reclaim, write-after-free, function pointer control, type confusion, or refcount takeover.
* No confidentiality or integrity impact in the conservative score. Possible UAF-like lifetime concern exists, but the concrete primitive is not demonstrated by the patch.

## 3. Reachability analysis

A local unprivileged process can plausibly trigger the affected path by using AF_UNIX sockets, descriptor passing behavior, and MSG_PEEK while AF_UNIX GC work is scheduled. No CAP_SYS_ADMIN, CAP_NET_ADMIN, or root privileges are normally required for basic AF_UNIX socket use. Containers and namespaces do not remove the concern because the bug is in host kernel AF_UNIX GC logic, although practical cross-container impact depends on namespace and socket usage patterns. The path is default-enabled on normal Linux systems and AF_UNIX is broadly deployed. Exploitation is still timing-dependent and the patch does not show a reliable privilege escalation primitive.

## 4. Severity interpretation

This behaves stronger than an ordinary Moderate because it is a local unprivileged race in a common kernel IPC subsystem involving GC and lifetime accounting. It is not a Strong Important candidate on the conservative evidence because the patch only shows gc_in_progress state inconsistency and GC confusion, not controlled memory reuse or an explicit write primitive. The best practical bucket is Actionable Moderate at minimum, with manual review justified due to AF_UNIX GC lifetime sensitivity.

## 5. One-sentence report phrase

A local unprivileged user may race AF_UNIX GC scheduling with MSG_PEEK so unix_gc runs while gc_in_progress is false, confusing GC lifetime handling and creating at least a local DoS risk with weak UAF concern.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK.

Reason: this is a race in AF_UNIX garbage collection and object lifetime handling in a default local IPC subsystem, with enough UAF-like concern to avoid auto-closing even though a concrete privilege escalation primitive is not demonstrated.

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

Patch: af_unix: Set gc_in_progress to true in unix_gc(). [ Upstream
Commit: 82c17e13d404f686e164590483fd6c1abaa675d0
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=82c17e13d404f686e164590483fd6c1abaa675d0

Changed files:
  net/unix/garbage.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=82c17e13d404f686e164590483fd6c1abaa675d0

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

The original Linux kernel CVE announcement for CVE-2026-53361 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53361

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:L/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:H/I:H/A:H
  The Best / paranoid CVSS score: 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: 4
  Paranoid ActionableScore: 5

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).