[CVE-2026-53352][LOW] signal: clear JOBCTL_PENDING_MASK for caller in zap_other_threads() [ Upstream

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

CVE: CVE-2026-53352
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: signal: clear JOBCTL_PENDING_MASK for caller in zap_other_threads() [ Upstream
Commit: 2b32b2fb241435145ea199efac024540759d2495
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2b32b2fb241435145ea199efac024540759d2495
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53352
Analysis date: Wed, 01 Jul 2026 10:08:48 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A local race between group-stop handling and execve() can leave stale JOBCTL flags on the surviving thread, causing a kernel WARN and potential local DoS on panic_on_warn systems, but no memory corruption or privilege escalation primitive is indicated.

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

The original Linux kernel CVE announcement for CVE-2026-53352 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53352

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-2026-53352	LOW	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:N/I:N/A:H';CWE-362;CWE-667;CWE-703;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A race in Linux signal handling can leave stale JOBCTL_STOP_PENDING and JOBCTL_STOP_CONSUME state on the execve caller when zap_other_threads aborts a pending group stop. After execve returns toward user mode, the caller may re enter do_signal_stop and task_participate_group_stop with signal group_stop_count already reset to zero, triggering a kernel WARN. For the CVSS the PR:L is used because a local unprivileged process can create threads and race execve against group stop handling in its own process context. The issue is not network reachable and requires local code execution. Impact is primarily local denial of service, especially on systems configured to panic on WARN. No UAF, OOB access, information leak, or privilege escalation primitive is indicated by the patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES	INIT WARNONLY RACE HARDWARE LINUS SYZBOT 	NO	NO	checked

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

ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local user can create a multithreaded process and race SIGSTOP or group-stop handling against execve().
* Broad/default/common subsystem: +1. This is core signal and execve handling, not a rare optional driver path.
* Hard or unreliable race / special timing required: -1. The issue depends on a narrow race between group-stop state and de_thread() / zap_other_threads() during execve().

Paranoid additional signal:

* Reliable kernel crash / strong DoS: +1. Only in the paranoid interpretation, because the observed effect is a WARN and it becomes a stronger DoS mainly on systems with panic_on_warn or if reliably repeatable.

Not counted:

* No remote reachable signal. The bug requires local process execution.
* No generic memory corruption. The patch fixes stale JOBCTL bookkeeping, not UAF, OOB, double-free, refcount misuse, or type confusion.
* No privilege escalation signal. No realistic LPE primitive is shown.
* No confidentiality or integrity impact. The effect is WARN / local DoS only.

## 3. Reachability analysis

A local unprivileged user can plausibly trigger the affected path by using threads, stop signals, and execve() in the same process context. Namespaces do not meaningfully reduce the required privilege because ordinary local code execution is enough, but they also do not create a cross-container or host-boundary bypass. The path is in default kernel signal handling and does not require a special driver or uncommon subsystem. Realistic exploitation requires winning a timing race and the practical impact is mainly a warning, or a crash on panic_on_warn systems.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like issue, not an Important-class vulnerability. Theoretical risk is limited because stale job-control state affects signal bookkeeping and the demonstrated failure mode is a WARN in task_participate_group_stop(). Realistic exploitation evidence supports local DoS only. There is no demonstrated memory corruption, information disclosure, file descriptor theft, namespace escape, or privilege escalation path.

## 5. One-sentence report phrase

A local race between group-stop handling and execve() can leave stale JOBCTL flags on the surviving thread, causing a kernel WARN and potential local DoS on panic_on_warn systems, but no memory corruption or privilege escalation primitive is indicated.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: the issue is local, race-dependent, and the patch context shows a WARN caused by stale signal bookkeeping rather than UAF, OOB access, corruption, or a security-boundary bypass.

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

Patch: signal: clear JOBCTL_PENDING_MASK for caller in zap_other_threads() [ Upstream
Commit: 2b32b2fb241435145ea199efac024540759d2495
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2b32b2fb241435145ea199efac024540759d2495

Changed files:
  kernel/signal.c
  arch/x86/kernel/signal.c
  kernel/entry/common.c
  arch/x86/entry/syscall_64.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=2b32b2fb241435145ea199efac024540759d2495

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

The original Linux kernel CVE announcement for CVE-2026-53352 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53352

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:L
  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: 1
  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).