[CVE-2026-74566][MODERATE 7.0] keys: make keyring key-chunk byte order agree with keyring_diff_objects() [ Upstream

[CVE-2026-74566][MODERATE 7.0] keys: make keyring key-chunk byte order agree with keyring_diff_objects() [ Upstream

[AL-KERNEL]

CVE: CVE-2026-74566
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: keys: make keyring key-chunk byte order agree with keyring_diff_objects() [ Upstream
Commit: bd0f976ef89dce6db458bf75bc2cf51127becc41
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bd0f976ef89dce6db458bf75bc2cf51127becc41
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74566
Analysis date: Sat, 15 Aug 2026 09:27:36 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum / not a Strong Important candidate from patch alone
Manual review required: NO

Summary:
A keyring index logic bug caused by mismatched byte order and bit-position calculation may allow crafted key descriptions to collide in one node, leading to local key lookup confusion with possible integrity and availability impact.

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

The original Linux kernel CVE announcement for CVE-2026-74566 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74566

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: NO

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

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

CVE-2026-74566	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';CWE-697;CWE-682;CWE-706;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '5.8';DESCR 'The keyring index can place crafted key descriptions incorrectly because keyring_get_key_chunk() and keyring_diff_objects() disagree on byte order and bit position. This may allow two distinct key descriptions to collide in the in-memory keyring lookup structure, which can cause key lookup confusion, shadowing, or failure to retrieve the intended key. For the CVSS the PR:L is used for the paranoid score because a local unprivileged process can normally create keys and crafted descriptions through keyctl or add_key, while reliable impact against another keyring still depends on keyring permissions. The issue is not directly network reachable and requires local interaction with the kernel key management API. Impact is primarily integrity and availability risk in key lookup behavior, with limited confidentiality impact possible in sensitive key management scenarios. It is not classified as proven memory corruption or direct privilege escalation from the patch alone.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum / not a Strong Important candidate from patch alone (with actual score 4)	YES	OOB SIMPLEFIX LINUS  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	YES	NO	checked

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

ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum / not a Strong Important candidate from patch alone**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. Local users can normally create keys and crafted descriptions through keyctl/add_key in keyrings they can write to.
* Integrity impact plausible: +1. Crafted descriptions may collide in the keyring index and cause key lookup confusion, shadowing, or incorrect placement.
* Broad/default/common subsystem: +1. Linux keyrings are a common core security subsystem, not a rare debug-only path.

Paranoid additional signals:

* Confidentiality impact plausible: +1. In sensitive shared keyring usage, lookup confusion could theoretically expose or select an unintended key, although this is not proven by the patch alone.
* Availability impact realistic: +1. Collisions or incorrect placement can plausibly break lookup/read behavior for affected keys and disrupt consumers relying on deterministic key resolution.

Not awarded:

* No remote reachable signal. This is local key management API behavior.
* No generic memory corruption signal. The patch shows byte-order and bit-position logic mismatch, not UAF, OOB write, double free, or arbitrary write.
* No privilege escalation signal. LPE is not demonstrated or strongly implied.
* No security-boundary bypass +2. A cross-keyring or cross-permission bypass is possible enough for review, but not sufficiently demonstrated for this stronger signal.

Call-site confidence: medium. The affected code is inside keyring assoc-array placement and comparison logic, but the supplied patch does not include all higher-level add/search call paths.

## 3. Reachability analysis

The bug is reachable by a local process that can create keys with crafted descriptions in a writable keyring. In typical deployments this is PR:L, not PR:H, because ordinary users often have access to their own user/session keyrings. Namespaces and containers can matter because containerized or service users may still have keyring API access, but impact against host or privileged keyrings depends on keyring permissions and sharing. The path is not network reachable by itself.

## 4. Severity interpretation

This behaves more like an actionable Moderate than ordinary Low because it affects security key management logic and crafted collisions may cause key lookup integrity issues. It is not an Important-class memory corruption issue from the patch alone. The realistic evidence supports local key confusion and possible service/key lookup disruption, while confidentiality or privilege escalation remains theoretical and requires manual validation of higher-level keyring consumers.

## 5. One-sentence report phrase

A keyring index logic bug caused by mismatched byte order and bit-position calculation may allow crafted key descriptions to collide in one node, leading to local key lookup confusion with possible integrity and availability impact.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED. YES REQUIRES MANUAL CHECK.

Manual review is recommended because the affected subsystem is security-sensitive and the practical impact depends on whether crafted key collisions can influence shared or privileged keyring lookups.

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

Patch: keys: make keyring key-chunk byte order agree with keyring_diff_objects() [ Upstream
Commit: bd0f976ef89dce6db458bf75bc2cf51127becc41
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bd0f976ef89dce6db458bf75bc2cf51127becc41

Changed files:
  security/keys/keyring.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=bd0f976ef89dce6db458bf75bc2cf51127becc41

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

The original Linux kernel CVE announcement for CVE-2026-74566 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74566

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:L/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 5.8

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: 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: NO
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).