* [CVE-2026-99004][MODERATE REGULAR] drm/imagination: Size page table preallocation by device address
@ 2026-10-26 18:40 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-10-26 18:40 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-99004
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/imagination: Size page table preallocation by device address
Commit: 51b56bad96fd20127034f660b337c00317c65151
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=51b56bad96fd20127034f660b337c00317c65151
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99004
Analysis date: Mon, 26 Oct 2026 14:40:32 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
A low-privilege DRM mapping can underflow the Imagination MMU table count and induce excessive allocation leading to host OOM panic, without evidence of memory corruption or authorization bypass.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99004 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99004
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: NO
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-99004 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-99004 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=MODERATE RESULT=DIFF (final Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC) 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-191;**CWE-400;CWE-770;BEST CVSS score: '5.5';DESCR 'An incorrect page table count in the Imagination DRM MMU path can make an unsigned index difference underflow when a device virtual mapping crosses a page table boundary. The resulting huge preallocation request can exhaust system memory and trigger an OOM panic, providing a local denial of service without evidence of an OOB access, UAF, information leak, or write primitive. For the CVSS the PR:L value reflects that an attacker needs local process access to the affected DRM render or device interface, while administrative privileges are not necessarily required when the render node is available. The issue is not directly network reachable and affects systems using the vulnerable Imagination GPU driver with an accessible mapping interface. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 5.5 and the production ActionableScore returned 2 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE_KPANIC to MODERATE because the CVSS score, vector or bug class threshold rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH and V41_INHERITED_KPANIC_PROMOTION_BLOCKED and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 5.5 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) MAYBE OOB DANGER SIMPLEFIX HARDWARE LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH V41_INHERITED_KPANIC_PROMOTION_BLOCKED MANUAL_REVIEW_REQUIRED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=2
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: 2.
* Conservative score: 2; no floor or cap applied.
* Raw paranoid score: 2.
* Paranoid score: 2; no defensible additional corrupt or boundary signal.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 Local low-privilege trigger: supplied triage evidence identifies access through an affected DRM render/device mapping interface without host-administrator powers.
* +1 Reliable kernel crash/strong DoS: the unsigned table-index subtraction can underflow, request a huge MMU-page preallocation, exhaust system memory, and trigger an OOM panic.
* No additional resource-exhaustion or Availability point: that would double-count the same OOM-panic outcome.
* No corruption point: the patch shows an incorrect allocation count, not an OOB read/write, UAF, stale pointer, or corrupted active object.
* NEW52/B5-R does not apply: there is no retry-accumulated index, confirmed heap OOB write, or later consumption of corrupted descriptors.
* No authorization, confidentiality, integrity, LPE, remote-reachability, or arbitrary-write signal is shown.
* No hardware rarity penalty: affected Imagination GPU hardware is required, but the evidence does not establish rare hardware or attacker physical access.
3. Reachability analysis
A local process with permission to use the affected DRM render/device mapping interface can supply a mapping crossing a page-table boundary. The supplied summary supports below-host-admin access through a render node, so host UID 0 and host-admin capabilities are not required for that deployment. No namespace capability is involved or shown. An affected GPU and driver are prerequisites; no boot option, race, retry loop, or prior privileged configuration is evidenced. Exact device-node permission and ioctl call-site details are not included.
4. Primitive and severity reading
The primitive is arithmetic underflow in page-table preallocation accounting, producing an excessive allocation request and possible host OOM panic. It is resource-exhaustion/DoS behavior, classified CLASS_C, rather than memory corruption. No post-allocation OOB operation or protected-state consumption is shown. Consequently there is no Important-preserving Class B/A primitive, and automatic downgrade remains allowed.
5. One-sentence report phrase
A low-privilege DRM mapping can underflow the Imagination MMU table count and induce excessive allocation leading to host OOM panic, without evidence of memory corruption or authorization bypass.
6. Manual review advice
MANUAL CHECK RECOMMENDED
Confirm affected render-node permissions and whether product OOM policy makes the exhaustion reliably host-fatal.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: drm/imagination: Size page table preallocation by device address
Commit: 51b56bad96fd20127034f660b337c00317c65151
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=51b56bad96fd20127034f660b337c00317c65151
Commit description:
Commit 0a82240 ("drm/imagination: Fix page count for page table for
map() interface") passed the device address to
pvr_mmu_op_context_create(), but the preallocation is still sized from
device_addr + sgt_offset with an exclusive end. The offset into the
object's pages has no place in a device-virtual range, and the exclusive
end allocates one table too many when the range ends on a table
boundary.
Count the tables from device_addr and the inclusive end of the range.
The new calculation does not take page table indices into account. This
fixes another issue with the previous implementation, where the
difference between start and end indices could underflow when a mapping
crossed a page table boundary. This would lead to the driver
preallocating a huge number of MMU pages, exhausting system memory and
triggering an out of memory panic.
Fixes: 0a82240 ("drm/imagination: Fix page count for page table for map() interface")
Fixes: ff5f643 ("drm/imagination: Add GEM and VM related code")
Signed-off-by: Gyeyoung Baek <[email protected]>
Reviewed-by: Brajesh Gupta <[email protected]>
Reviewed-by: Alessio Belle <[email protected]>
Cc: [email protected]
[Alessio: add paragraph to point out OOM bug being fixed, cc stable]
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Alessio Belle <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/gpu/drm/imagination/pvr_mmu.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=51b56bad96fd20127034f660b337c00317c65151
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99004 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99004
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: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: unknown
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: 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).
^ permalink raw reply [relevance 21%]
Results 1-1 of 1 | reverse | sort options + mbox downloads above
-- links below jump to the message on this page --
2026-10-26 18:40 21% [CVE-2026-99004][MODERATE REGULAR] drm/imagination: Size page table preallocation by device address AL-KERNEL
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox