* [CVE-2026-89872][LOW] media: v4l2-fwnode: Fix fwnode leak in v4l2_fwnode_parse_link
@ 2026-09-16 17:14 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-16 17:14 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-89872
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: media: v4l2-fwnode: Fix fwnode leak in v4l2_fwnode_parse_link
Commit: c9b5238d173ee9b94dcaa2b34244ea89c8024feb
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c9b5238d173ee9b94dcaa2b34244ea89c8024feb
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89872
Analysis date: Wed, 16 Sep 2026 13:14:40 -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-2026-89872 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89872
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-2026-89872 LOW https://www.kernelcve.org/list/?q=CVE-2026-89872 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:H/UI:N/S:U/C:N/I:N/A:H';*CWE-772;*CWE-401;CWE-404;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'V4L2 fwnode link parsing leaks a firmware node reference on the successful return path of v4l2_fwnode_parse_link(). The issue is a reference leak and resource management bug rather than a memory corruption primitive. Repeated probe or reprobe of affected media devices could accumulate leaked references and eventually contribute to resource exhaustion. For the CVSS the PR:H is used because reliable triggering typically requires administrative control over driver loading, device reprobe, hotplug, or firmware description used by the media device. The issue is not network reachable. Impact is denial of service only, normally limited availability impact unless repeated triggering is practical in the target environment.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) YES SIMPLEFIX LEAK ERRORPATH HARDWARE NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=0
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: -1
* Conservative score: 0
* Raw paranoid score: -1
* Paranoid score: 0
* Applied conservative floor/cap: score clamped from -1 to 0.
* Applied paranoid floor/cap: score clamped from -1 to 0.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
Positive signals:
* +1 Concrete persistent kernel resource/reference leak. The patch directly shows that a fwnode reference acquired by fwnode_graph_get_remote_endpoint() was not released on the successful return path of v4l2_fwnode_parse_link().
* +0 Resource exhaustion beyond the reference leak is not separately awarded. Repeated probe or reprobe could accumulate leaked references, but no evidence shows immediate or practical host-wide exhaustion from a low-privilege attacker.
Negative signals:
* -2 Host-admin-equivalent triggering requirement. Reliable triggering appears to require administrative control over driver probing, reprobing, hotplug, module/device management, or firmware/device-description state.
Important non-awarded signals:
* RealUAF not awarded. This is a missing put/reference leak, not a stale post-free use.
* Concrete repeated release/refcount not awarded. The bug is missing fwnode_handle_put(), not a second put on a dangling reference.
* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* Confidentiality and integrity impact not awarded.
* Remote reachability not established.
* Local unprivileged trigger not established.
* Extra availability not awarded because practical host-wide exhaustion is not established.
* ImportantCandidate not awarded because the primitive is a constrained resource/reference leak with host-admin-level triggering.
3. Reachability analysis
The vulnerable path is in V4L2 firmware-node link parsing, typically reached during media device probe or related driver initialization paths. A practical attacker would need to cause repeated successful parsing of affected fwnode links, which normally implies control over driver loading, device reprobe, hotplug behavior, or firmware description such as device tree or ACPI data.
Ordinary local unprivileged reachability is not established. Namespace-scoped privilege is not applicable from the supplied evidence. There is no network trigger. No special remote packet path or userspace data-plane API is shown. The relevant operations are local device-management and initialization paths, so HostAdminRequired=YES is used.
No race is involved. No special rare hardware penalty is separately applied beyond the already counted host-admin/device-management requirement.
4. Primitive and severity interpretation
The exact primitive is a persistent fwnode reference leak on the success path of v4l2_fwnode_parse_link(). The acquired remote endpoint reference is not released until the patch adds fwnode_handle_put() before return 0.
This is not an active structured UAF and not fixed stale storage. It is a resource/lifetime accounting defect without post-lifetime dereference. There is no concrete repeated release/refcount operation. The first lifetime operation is an acquire/get. The missing second operation is a release/put, not a stale mutation through freed storage.
PrimitiveClass=NONE because no meaningful corruption, UAF, ownership violation, authorization bypass, or security-boundary primitive is established. The demonstrated consequence is a reference leak. The speculative consequence is gradual resource exhaustion if an administrator or privileged management path repeatedly reprobes affected devices. There is no supported privilege escalation, information disclosure, arbitrary write, or memory-corruption primitive.
ImportantCandidate=NO because the issue is a constrained resource leak. AutoDowngradeAllowed=YES because no unresolved kernel-corruption or boundary-bypass primitive remains.
Likely operational severity is Low-like or ordinary Moderate at most.
5. One-sentence report phrase
V4L2 fwnode link parsing leaks a remote endpoint reference on the successful return path, and repeated privileged probe or reprobe activity may accumulate leaked references but no UAF, memory corruption, network trigger, or privilege escalation primitive is established.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The issue is a straightforward reference leak with host-admin-level triggering and no evidence of UAF, repeated stale refcount mutation, authorization bypass, or controlled corruption.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: media: v4l2-fwnode: Fix fwnode leak in v4l2_fwnode_parse_link
Commit: c9b5238d173ee9b94dcaa2b34244ea89c8024feb
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c9b5238d173ee9b94dcaa2b34244ea89c8024feb
Commit description:
In v4l2_fwnode_parse_link(), the remote endpoint fwnode reference is
acquired using fwnode_graph_get_remote_endpoint(). This reference is
properly released in the error paths, but it is leaked on the success
path.
Add the missing fwnode_handle_put() before returning 0 to prevent the
reference leak.
Signed-off-by: Biren Pandya <[email protected]>
Fixes: ca50c19 ("[media] v4l: fwnode: Support generic fwnode for parsing standardised properties")
Cc: [email protected]
[Sakari Ailus: Fix subject prefix and coding style a little.]
Signed-off-by: Sakari Ailus <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/media/v4l2-core/v4l2-fwnode.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=c9b5238d173ee9b94dcaa2b34244ea89c8024feb
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89872 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89872
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:L/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:H
The Best / paranoid CVSS score: 4.4
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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