* [CVE-2026-93234][LOW] drm/gud: validate TV mode names before creating enum property
@ 2026-09-24 16:14 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-24 16:14 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-93234
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/gud: validate TV mode names before creating enum property
Commit: 676f1fb3632bbc9ce83be7938e93fe6bfc9510fd
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=676f1fb3632bbc9ce83be7938e93fe6bfc9510fd
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93234
Analysis date: Thu, 24 Sep 2026 12:14:43 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-93234 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93234
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-2026-93234 LOW https://www.kernelcve.org/list/?q=CVE-2026-93234 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N';*CWE-20;CWE-170;*CWE-20;CWE-170;BEST CVSS score: '0';DESCR 'The shown pre patch code already writes a NUL byte to the last position of every fixed size TV mode name slot before the value reaches strlen. Therefore a malformed GUD device response without a NUL terminator is truncated within its own slot and does not demonstrate an out of bounds read from the supplied code. The issue is a protocol validation weakness because malformed TV mode names are accepted and silently modified instead of being rejected. No confidentiality integrity or availability impact is supported by this patch context. ';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) YES OOB DANGER SIMPLEFIX HARDWARE SYZBOT DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=0
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 0
* Conservative score: 0
* Raw paranoid score: 0
* Paranoid score: 0
* Final recommended bucket: **Ordinary Moderate**::
No floor or cap was applied.
2. Signal breakdown
* 0: No concrete OOB read is established by the supplied pre-patch diff. The old code writes a NUL byte at `mode[GUD_CONNECTOR_TV_MODE_NAME_LEN - 1]` before the string reaches `strlen()`.
* 0: No UAF, stale reference, refcount misuse, overwrite, disclosure path, authorization bypass, or crash is established.
* 0: The changed behavior is protocol validation. Malformed fixed-size TV mode names were previously accepted after in-place truncation and are now rejected with `-EIO`.
* 0: No confidentiality impact is awarded because no bytes beyond the slot are shown to be read.
* 0: No integrity impact is awarded because the old NUL write is bounded within the fixed-size slot.
* 0: No availability impact is awarded because the supplied code does not demonstrate a kernel fault, hang, reset, or resource exhaustion.
Important non-awarded signals:
* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* Remote reachability not established.
* No lifetime or repeated release/refcount operation exists.
* No disclosure path exists.
* No kernel memory corruption primitive exists.
3. Reachability analysis
A malformed TV mode name originates from a GUD USB display device response. A physical attacker who can connect or emulate such a USB device would not normally need host-admin privileges for the device to be enumerated, therefore `HostAdminRequired=NO` for the physical-device input path.
However, the complete supplied pre-patch code bounds the string by forcibly inserting a NUL byte into the final byte of each fixed-size mode-name slot. Therefore malformed device input does not reach `strlen()` without a terminator. Namespace-scoped privilege is not relevant to this USB device protocol path and remains `UNKNOWN`.
No network trigger, ordinary userspace trigger, attacker-controlled kernel memory layout, or DRM master operation is required by the demonstrated behavior. The issue is not dependent on a race.
4. Primitive and severity interpretation
The supplied commit message describes a potential out-of-bounds read, but the supplied pre-patch diff contradicts that claim. The removed code explicitly ensures that every fixed-size entry is NUL-terminated before the entry is later consumed as a C string.
The actual demonstrated change is from silently truncating malformed protocol input to rejecting malformed input. This is an input-validation and protocol-conformance improvement, not an established memory-corruption fix.
Primitive class is `NONE`. There is no real UAF, no active structured stale object, no cleanup/destructor lifetime issue, no repeated release/refcount mutation, and no demonstrated crash-only primitive. No meaningful exploitation leverage beyond malformed device-response acceptance is present.
`ImportantCandidate=NO` because no concrete security primitive remains unresolved. `AutoDowngradeAllowed=YES` because the supplied code supports no memory-safety, ownership, authorization, or availability consequence requiring manual investigation.
Likely operational severity is non-security protocol hardening unless a different affected parent revision lacks the removed bounded NUL-termination statement or has an independently incorrect buffer allocation.
5. One-sentence report phrase
The supplied pre-patch code already NUL-terminates each fixed-size GUD TV mode name slot, so this change rejects malformed protocol data instead of silently truncating it and does not establish an out-of-bounds read.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The visible pre-patch bounds enforcement prevents the alleged `strlen()` over-read, and no separate corruption or disclosure primitive is shown.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: drm/gud: validate TV mode names before creating enum property
Commit: 676f1fb3632bbc9ce83be7938e93fe6bfc9510fd
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=676f1fb3632bbc9ce83be7938e93fe6bfc9510fd
Commit description:
The GUD protocol returns TV mode names as fixed-size
GUD_CONNECTOR_TV_MODE_NAME_LEN entries and requires each name to be
NUL-terminated.
gud_connector_add_tv_mode() currently passes each fixed-size entry
directly to drm_mode_create_tv_properties_legacy(), which eventually
reaches drm_property_add_enum() and strlen(). If a device returns an
entry without a terminating NUL byte, strlen() reads past the end of
the slot and can run beyond the allocated buffer, triggering an
out-of-bounds read.
Validate that each returned TV mode name contains a NUL terminator
within its fixed-size slot before passing it to the DRM property code.
If a malformed entry is found, reject the device response with -EIO.
This fixes the out-of-bounds read without changing the handling of
valid devices, and avoids silently truncating malformed protocol data.
Reported-by: [email protected]
Fixes: 40e1a70 ("drm: Add GUD USB Display driver")
Signed-off-by: Tao Yu <[email protected]>
Reviewed-by: Ruben Wauters <[email protected]>
Cc: <[email protected]>
Signed-off-by: Ruben Wauters <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/gpu/drm/gud/gud_connector.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=676f1fb3632bbc9ce83be7938e93fe6bfc9510fd
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-93234 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93234
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: Not available
The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N
The Best / paranoid CVSS score: 0
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: unknown
Paranoid ActionableScore: 0
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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