* [CVE-2026-89900][LOW] media: cec: core: Fix kmemleak due to missed rc_free_device() call
@ 2026-09-16 18:33 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-16 18:33 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-89900
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: media: cec: core: Fix kmemleak due to missed rc_free_device() call
Commit: 954ee95a03b4d31d4505591bfaba02c24b75776b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=954ee95a03b4d31d4505591bfaba02c24b75776b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89900
Analysis date: Wed, 16 Sep 2026 14:33:39 -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-2026-89900 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89900
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-2026-89900 LOW https://www.kernelcve.org/list/?q=CVE-2026-89900 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-401;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'The CEC core can leak an allocated rc device because cec_unregister_adapter cleared adap rc after rc_unregister_device, preventing the later rc_free_device path from seeing the pointer. The issue can be observed during adapter removal or driver unbind cycles such as dw hdmi unbind and can accumulate memory over repeated device teardown operations. For the CVSS the PR:H is used because reliable triggering normally requires administrative control over driver bind unbind or device removal. The issue is not network reachable and does not provide a direct memory corruption primitive. Impact is denial of service only through resource exhaustion if the leak is repeated many times.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) MAYBE INIT RACE LEAK HARDWARE DEBUGFS LINUS - - 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: 0
* Paranoid score: 0
* Conservative lower bound applied: -1 -> 0
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 Concrete persistent kernel resource/reference leak. The patch directly establishes that an allocated rc device becomes unreachable from normal cleanup because adap->rc is cleared before the later rc_free_device path can use it.
* -2 Host-admin-equivalent triggering requirement. The demonstrated trigger is adapter removal or driver unbind, e.g. dw-hdmi unbind, which is a host device-management operation normally requiring host administrator privileges.
* Paranoid +1 resource-exhaustion interpretation. Repeated bind/unbind or probe/remove cycles could accumulate the leak and eventually consume memory, but this remains a resource leak without corruption.
* No Real UAF awarded. The object is leaked, not used after being freed.
* No concrete repeated release/refcount signal. There is no established first release that may end lifetime followed by a second lifetime mutation on the same dangling reference.
* No reliable kernel crash signal. The supplied evidence is kmemleak output, not panic/Oops.
* No C/I impact. There is no disclosure path, arbitrary write, ownership violation, or security-boundary bypass.
* No remote reachability. HDMI/CEC driver teardown is not network-triggered.
* No structured stale-object leverage. The bug prevents cleanup of an object rather than consuming attacker-shaped stale fields.
* No manual-review escalation. This is a host-admin-gated persistent memory leak with no memory corruption primitive.
3. Reachability analysis
The practical trigger is local host device management, such as unbinding the dw-hdmi related device or otherwise removing/unregistering the CEC adapter. That operation is normally controlled through host sysfs or driver core mechanisms and requires host administrator privileges. Ordinary local users may use CEC device interfaces in some deployments, but the supplied evidence does not show that they can perform the complete vulnerable unregister/unbind sequence.
Namespace-scoped privilege is not established. The affected object is a media/CEC rc device tied to a host hardware driver path, not a namespace-local object. No network vector, container-only trigger, sysctl bypass, boot parameter dependency, or remote device input path is shown. Special hardware exists in the sense that a CEC-capable HDMI/media device is involved, but the main reducing factor is host-admin device-management reachability, not rare hardware.
4. Primitive and severity interpretation
The exact primitive is a persistent kernel object leak caused by clearing adap->rc too early. This prevents the later CEC adapter cleanup path from reaching the allocated rc device and calling rc_free_device. It is not an active structured UAF, not fixed stale storage, not a double free, and not a concrete repeated refcount mutation.
Demonstrated consequence is memory leakage detected by kmemleak. The speculative worst case is resource-exhaustion DoS if an administrator or privileged management process repeatedly drives adapter teardown cycles. There is no patch-supported path to privilege escalation, information disclosure, arbitrary write, controlled reclaim, callback hijack, or authorization bypass.
PrimitiveClass is NONE because no meaningful corruption, stale lifetime use, ownership violation, or authorization primitive is established. ImportantCandidate is NO because the issue is a constrained host-admin-gated resource leak. AutoDowngradeAllowed is YES because automatic downgrade would not discard an unresolved corruption or security-boundary primitive.
5. One-sentence report phrase
The CEC core can leak an allocated rc device during adapter unregister because adap->rc is cleared before the later rc_free_device cleanup path can see it, making the practical impact host-admin-triggered resource exhaustion only.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
This can be treated as an ordinary low-severity resource leak because it requires host device-management privileges and has no evidence of UAF, double release, memory corruption, disclosure, privilege escalation, or network reachability.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: media: cec: core: Fix kmemleak due to missed rc_free_device() call
Commit: 954ee95a03b4d31d4505591bfaba02c24b75776b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=954ee95a03b4d31d4505591bfaba02c24b75776b
Commit description:
The commit dccc0c3 ("media: rc: fix race between unregister and
urb/irq callbacks") removed the implicit call to rc_free_device() from
rc_unregister_device(). However, the commit missed to remove the NULL
assignment of adap->rc that is now causing rc_free_device() to never be
called on an allocated rc device.
kmemleak reports following after e.g. dw-hdmi unbind:
unreferenced object 0xffff00010ac10000 (size 4096):
comm "kworker/u16:1", pid 39, jiffies 4294897739
hex dump (first 32 bytes):
20 23 4b 0a 01 00 ff ff 08 00 c1 0a 01 00 ff ff #K.............
08 00 c1 0a 01 00 ff ff 00 00 00 00 00 00 00 00 ................
backtrace (crc e11baccc):
kmemleak_alloc+0x38/0x44
__kmalloc_cache_noprof+0x4a8/0x5e0
rc_allocate_device+0x48/0x2a0
cec_allocate_adapter+0x3ac/0x800
dw_hdmi_cec_probe+0x264/0x634
platform_probe+0xc0/0x188
really_probe+0x4a4/0x8e0
__driver_probe_device+0x2f8/0x440
driver_probe_device+0x60/0x160
__device_attach_driver+0x1a0/0x2a0
bus_for_each_drv+0x100/0x1a0
__device_attach+0x174/0x350
device_initial_probe+0x90/0xb0
bus_probe_device+0x4c/0x120
device_add+0xdec/0x116c
platform_device_add+0x354/0x598
Remove the assignment of adap->rc to NULL to let cec_delete_adapter()
free the allocated rc device after last user of the cec device exits to
fix the kmemleak.
Fixes: dccc0c3 ("media: rc: fix race between unregister and urb/irq callbacks")
Cc: [email protected]
Signed-off-by: Jonas Karlman <[email protected]>
Signed-off-by: Hans Verkuil <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/media/cec/core/cec-core.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=954ee95a03b4d31d4505591bfaba02c24b75776b
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89900 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89900
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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