* [CVE-2026-98516][LOW] drm/nouveau: Fix bridge reference leak in nv1a_ram_new()
@ 2026-10-19 8:20 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-19 8:20 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98516
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/nouveau: Fix bridge reference leak in nv1a_ram_new()
Commit: add5e0a45e3971df9c65cc7b59c90559a25dc5a9
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=add5e0a45e3971df9c65cc7b59c90559a25dc5a9
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98516
Analysis date: Mon, 19 Oct 2026 04:20:04 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
The nouveau nv1a RAM initialization path leaks a PCI bridge reference by failing to balance pci_get_domain_bus_and_slot with pci_dev_put, but no practical host-wide exhaustion, memory corruption, or security-boundary consequence is established.
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ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98516 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98516
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.
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AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-98516 LOW https://www.kernelcve.org/list/?q=CVE-2026-98516 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT LOW AEGIS_AS=1 LEGACY=LOW RESULT=SAME (final reconciliation agrees; DECISION: both LOW) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';*CWE-772;*CWE-401;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '2.3';DESCR 'A PCI device reference leak occurs in nouveau because nv1a_ram_new obtains a bridge reference through pci_get_domain_bus_and_slot but does not release it after reading the memory configuration. The demonstrated primitive is persistent reference retention rather than memory corruption, and the code does not show a UAF, OOB access, information disclosure, or write primitive. For the CVSS the PR:H reflects that reliable repeated triggering normally requires administrative control over driver probing, device binding, or GPU reset operations. The issue is not network reachable. Repeated initialization may increase the bridge reference count and delay object release, but immediate memory exhaustion or a host wide denial of service is not established. Impact is therefore limited to a low availability risk. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 2.3 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. No severity changing production threshold or specialist override was recorded. 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. The independent weaker Aegis shadow evaluated CVSS 2.4 and ActionableScore 1 with primitive class CLASS_C and manual review NO. Its independently reconciled impact was LOW. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) MAYBE READ SIMPLEFIX LEAK HARDWARE LINUS - - checked
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ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=1
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 Concrete persistent kernel resource/reference leak. `pci_get_domain_bus_and_slot()` acquires a reference to the PCI bridge, and the original path permanently loses that reference without calling `pci_dev_put()`.
* No reliable kernel crash point. The patch does not establish panic, Oops, device failure, or host-wide unavailability.
* No additional resource-exhaustion point. Repeated initialization could increase the reference count, but no per-invocation object allocation, practical exhaustion mechanism, or persistent host-wide pressure is demonstrated.
* No corruption point. There is no OOB access, UAF, stale dereference, double release, active-state overwrite, or attacker-controlled write.
* No authorization or trust-boundary point. The patch changes resource cleanup only and contains no DENY-to-ALLOW decision.
* NEW52 B5-R does not apply. There is no heap OOB write, retry-accumulated offset, or later consumption of corrupted structured state.
* NEW53 B3-PENDING does not apply. There is no write to shared or file-backed storage.
* V33 and V34 do not apply. No attacker-influenced active structured state is corrupted.
* B4-PENDING does not apply. No security guard, protected resource, or attacker-invocable authorization path is involved.
* Remote reachability, confidentiality impact, integrity impact, LPE, controlled reclaim, and arbitrary write are not established.
3. Reachability analysis
The reference is acquired while `nv1a_ram_new()` initializes RAM information for supported nouveau hardware. Initial driver probing can occur automatically, but the supplied evidence does not establish an attacker-controlled interface that repeatedly invokes this function.
Reliable accumulation would likely require repeated host-level device probing, binding, reset, or driver reinitialization. The exact complete trigger and its privilege checks are not supplied, so `HostAdminRequired` remains `UNKNOWN` rather than assuming either host administration or below-host-admin access.
No user-namespace or device-namespace path is established. PCI device management is host-global, but the evidence does not show the complete operation used to repeat the leak. Prior presence of compatible nouveau hardware and the relevant bridge is required. There is no race or network trigger.
4. Primitive and severity interpretation
The exact defect is an unbalanced PCI device reference:
`pci_get_domain_bus_and_slot()`
`-> reference acquired`
`-> bridge configuration read`
`-> function returns without pci_dev_put()`
This retains the referenced PCI device object longer than intended. It does not free the object prematurely, leave a dangling pointer, or perform a second lifetime mutation through freed storage. Therefore, it is not a UAF and not a concrete repeated-release case.
The retained reference may prevent final release of the bridge object after device removal. However, the patch does not demonstrate practical memory exhaustion, refcount takeover, host crash, or corruption of active state. Incrementing the same reference count is not equivalent to allocating a new leaked object on every invocation.
`PrimitiveClass=NONE` is appropriate because the established behavior is resource retention without a corruption, authorization, ownership, or useful lifetime-violation primitive. `ImportantCandidate=NO` and `AutoDowngradeAllowed=YES` follow because no unresolved Important-preserving mechanism exists. The likely operational severity is Low-like.
5. One-sentence report phrase
The nouveau nv1a RAM initialization path leaks a PCI bridge reference by failing to balance pci_get_domain_bus_and_slot with pci_dev_put, but no practical host-wide exhaustion, memory corruption, or security-boundary consequence is established.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The patch fixes a narrow and concrete reference leak with no demonstrated attacker-controlled accumulation, corruption, crash, or protected-resource impact.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: drm/nouveau: Fix bridge reference leak in nv1a_ram_new()
Commit: add5e0a45e3971df9c65cc7b59c90559a25dc5a9
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=add5e0a45e3971df9c65cc7b59c90559a25dc5a9
Commit description:
pci_get_domain_bus_and_slot() takes a reference to the PCI device,
which is never released once the memory size has been read from its
config space. Drop the reference before returning.
Fixes: 2fa6d6c ("drm/nouveau: deprecate pci_get_bus_and_slot()")
Cc: [email protected]
Signed-off-by: Wentao Liang <[email protected]>
Reviewed-by: Lyude Paul <[email protected]>
Signed-off-by: Lyude Paul <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/gpu/drm/nouveau/nvkm/subdev/fb/ramnv1a.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=add5e0a45e3971df9c65cc7b59c90559a25dc5a9
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98516 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98516
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:H/UI:N/S:U/C:N/I:N/A:L
The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L
The Best / paranoid CVSS score: 2.3
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: 1
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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