* [CVE-2026-93139][MODERATE REGULAR] drm/amdgpu/mes: Fix hung_queue_db_array loop limit for multi-XCC [ Upstream
@ 2026-09-18 5:13 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-18 5:13 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-93139
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/amdgpu/mes: Fix hung_queue_db_array loop limit for multi-XCC [ Upstream
Commit: 7ff668cfc3960ed5b944ac35129f18a15ea08b74
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7ff668cfc3960ed5b944ac35129f18a15ea08b74
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93139
Analysis date: Fri, 18 Sep 2026 01:13:20 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline / manual review recommended
Manual review required: YES
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-93139 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93139
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-2026-93139 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-93139 CHECK WITH IMPACT FROM ORIG NN LOW 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:N/A:H';CWE-824;**CWE-476;CWE-665;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'amdgpu MES initialized hung_queue_db_array only for AMDGPU_MAX_MES_PIPES entries even on multi XCC GPUs where later accesses can use indexes across AMDGPU_MAX_MES_PIPES times num_xcc. On affected systems, entries for XCC ID 2 or higher may remain uninitialized and later be dereferenced as NULL, causing a kernel crash. For the CVSS the PR:L is used because a local user with access to the DRM render node may be able to submit GPU work or exercise amdgpu paths that reach MES hang handling without full administrator privileges. The issue is not network reachable and requires local GPU access plus specific AMD multi XCC hardware. Impact is denial of service via kernel crash. No confidentiality or integrity impact is assigned because the primitive is a NULL pointer dereference rather than a demonstrated UAF, OOB write, or arbitrary write.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) SKIP CVE-2026-93139 UNKNOWN SKIP No affected files built, so skip this CVE NO - - unknown MAYBE NULLPTR SIMPLEFIX HARDWARE MEMORY DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=3
ActionableScoreLower=2
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 2
* Conservative score: 2. No floor or cap applied.
* Raw paranoid score: 3
* Paranoid score: 3. No floor or cap applied.
* Final recommended bucket: **Borderline / manual review recommended**::
2. Signal breakdown
Conservative positive signals:
* +1 Reliable kernel crash / strong DoS: the commit states that uninitialized hung_queue_db_array entries can cause NULL pointer dereferences when XCC ID >= 2 is accessed.
* +1 Weak / indirect corruption candidate: the bug is incomplete initialization of an array of kernel objects or pointers, causing invalid NULL dereference through later indexing.
Conservative negative signals:
* No negative privilege penalty: host-admin-equivalent triggering is not positively established.
* No hardware penalty applied: the issue requires AMD multi-XCC GPUs, but the supplied evidence does not prove rare or physical-only attacker interaction beyond the affected host having such hardware.
Paranoid additional signal:
* +1 Possible below-host-admin DRM/GPU reachability: local users with DRM render-node access may be able to submit GPU work or exercise paths that reach MES hang handling, but the complete trigger path is not fully established.
Material non-awarded signals:
* RealUAF not awarded: the patch establishes uninitialized array entries and NULL pointer dereference, not post-lifetime object use.
* Controlled reclaim not demonstrated.
* Arbitrary or directed kernel write not demonstrated.
* Confidentiality and integrity not awarded: there is no disclosure, OOB write, UAF reuse, or attacker-controlled object corruption primitive.
* Remote reachability not established.
* Structured stale-object leverage not awarded because no stale object exists.
* Concrete repeated release/refcount not awarded because there is no first release, surviving reference, and second lifetime mutation.
* Extra availability not awarded because the same NULL dereference crash is already counted once.
* ImportantCandidate not set because the demonstrated primitive is crash-only Class C.
3. Reachability analysis
The immediate vulnerable condition is created during amdgpu MES initialization on multi-XCC GPUs. The commit says the loop initializes only AMDGPU_MAX_MES_PIPES entries while later access can index across AMDGPU_MAX_MES_PIPES * num_xcc, leaving entries for XCC ID >= 2 uninitialized.
The likely attacker model is local. A local graphics user, compositor, display service, or process with access to DRM render nodes may be able to exercise GPU submission or hang-handling paths, but the supplied patch does not prove the complete path from an ordinary user to the exact NULL dereference. Therefore HostAdminRequired is UNKNOWN rather than NO.
For DRM/KMS roles:
* Ordinary logged-in user: possible only if render-node access and relevant workload path reach MES hang handling, not fully proven here.
* DRM master or compositor/display server: more plausible, but still not fully shown by the diff.
* Delegated graphics/display service: plausible if it can submit workloads to the affected GPU.
* Host administrator: can clearly load, configure, and exercise the driver, but host-admin requirement is not positively established as mandatory.
Namespace-scoped privilege is not relevant from the supplied evidence. No network trigger is indicated. Prior hardware prerequisite exists: the system must use an affected AMD multi-XCC GPU and the amdgpu MES path must be active. No race is required.
4. Primitive and severity interpretation
The exact primitive is incomplete initialization of hung_queue_db_array for multi-XCC devices. Later code can index entries corresponding to XCC ID >= 2 and dereference an uninitialized or NULL entry, producing a kernel NULL pointer dereference.
This is not active structured UAF and not fixed stale storage. It is a Class C invalid-state / NULL-dereference issue. The demonstrated consequence is local denial of service via kernel crash. The speculative consequence beyond crash is weak: no evidence shows UAF, OOB write, attacker-controlled replacement object, callback control, page ownership corruption, or privilege escalation.
ImportantCandidate is NO because the patch supports crash-only behavior without a meaningful unresolved corruption primitive. AutoDowngradeAllowed is YES because no Class A primitive, no Class B lifetime issue, and no security-boundary bypass is established. Operational severity is borderline to ordinary Moderate, with manual review recommended mainly to confirm real user reachability on affected AMD multi-XCC GPUs.
5. One-sentence report phrase
An incomplete initialization bug in amdgpu MES on multi-XCC GPUs can leave hung_queue_db_array entries for XCC ID >= 2 unset, allowing later GPU driver paths to hit a NULL pointer dereference and cause a local kernel crash.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
Reason: the issue is likely DoS-only, but review should confirm whether an ordinary render-node user can reliably reach the MES hang-handling access path on affected multi-XCC AMD GPUs.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: drm/amdgpu/mes: Fix hung_queue_db_array loop limit for multi-XCC [ Upstream
Commit: 7ff668cfc3960ed5b944ac35129f18a15ea08b74
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7ff668cfc3960ed5b944ac35129f18a15ea08b74
Changed files:
drivers/gpu/drm/amd/amdgpu/amdgpu_mes.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=7ff668cfc3960ed5b944ac35129f18a15ea08b74
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-93139 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93139
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:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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: 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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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