[CVE-2026-80776][MODERATE REGULAR] futex: Fix race in futex_pivot_pending() during private hash resize [ Upstream

[CVE-2026-80776][MODERATE REGULAR] futex: Fix race in futex_pivot_pending() during private hash resize [ Upstream

[AL-KERNEL]

CVE: CVE-2026-80776
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: futex: Fix race in futex_pivot_pending() during private hash resize [ Upstream
Commit: 4a7e941ca29a608c6244cbd028d3599ecaef7207
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4a7e941ca29a608c6244cbd028d3599ecaef7207
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80776
Analysis date: Fri, 04 Sep 2026 14:38:09 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
A race in futex_pivot_pending during private futex hash resize can cause a local process to miss a completed pivot wakeup and remain stuck in uninterruptible sleep, potentially causing a kernel panic when hung task panic is enabled.

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

The original Linux kernel CVE announcement for CVE-2026-80776 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80776

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.

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

CVE-2026-80776	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80776 CHECK WITH IMPACT FROM ORIG NN LOW	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-400;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 futex_pivot_pending can make a private futex hash resize task miss the final wakeup and remain blocked in uninterruptible sleep. The bug comes from reading hash_new and hash without serialization, allowing the task to observe a mixed pre pivot and post pivot state and incorrectly decide that the pivot is still pending. For the CVSS the PR:L is used because a local process is required to invoke the private hash resize path and create the futex activity needed for reliable triggering. AC:H is used because the failure depends on a race window between the resize waiter and another futex task completing the pivot. The issue is not network reachable. Impact is denial of service through a stuck D state task and in configurations with hung task panic it can cause a kernel panic.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 3)	YES	WARNONLY RACE  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	YES	NO	checked

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

ActionableScore=3
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 3
* Final recommended bucket: **Borderline, manual review recommended**

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local process can reach the private futex hash resize path through the prctl syscall path shown in the trace.
* Availability impact realistic: +1. The task can remain stuck in uninterruptible sleep indefinitely.
* Broad/default/common subsystem: +1. Futex is core kernel synchronization infrastructure.
* Hard or unreliable race / special timing required: -1. The issue depends on observing mixed pre-pivot and post-pivot state across a narrow race window.

Paranoid additional interpretation:

* Reliable kernel crash / strong DoS: +1. If hung_task_panic or similar policy is enabled, the stuck D-state task can escalate from local task hang to kernel panic.

No memory corruption, UAF, OOB write, refcount takeover, stale callback, or privilege escalation primitive is supported by the patch.

## 3. Reachability analysis

The bug is locally reachable by a process that can invoke the private futex hash resize path and create concurrent futex activity in the same mm. Namespaces or containers may not prevent triggering if the relevant prctl and futex operations are exposed to the container workload. The issue is not network reachable. The affected subsystem is common, but the specific private hash resize path is a narrower futex feature and reliable triggering requires race timing.

## 4. Severity interpretation

This behaves like a local DoS race, not an Important-class memory corruption issue. The realistic impact is an indefinitely blocked task, with possible system-wide panic only under hung-task panic configuration. Theoretical escalation is not supported because the patch only serializes inconsistent state observation and does not show stale object reuse, write-after-free, type confusion, callback control, or attacker-controlled memory reuse.

## 5. One-sentence report phrase

A race in futex_pivot_pending during private futex hash resize can cause a local process to miss a completed pivot wakeup and remain stuck in uninterruptible sleep, potentially causing a kernel panic when hung task panic is enabled.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED. This is core futex synchronization code and a race condition, but the available evidence supports DoS only and does not justify treating it as memory corruption or privilege escalation.

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

Patch: futex: Fix race in futex_pivot_pending() during private hash resize [ Upstream
Commit: 4a7e941ca29a608c6244cbd028d3599ecaef7207
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4a7e941ca29a608c6244cbd028d3599ecaef7207

Changed files:
  kernel/futex/core.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=4a7e941ca29a608c6244cbd028d3599ecaef7207

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

The original Linux kernel CVE announcement for CVE-2026-80776 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80776

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: 2
  Paranoid ActionableScore: 3

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).