* [CVE-2026-97985][LOW] af_unix: Update last skb marker in manage_oob(). [ Upstream
@ 2026-09-26 20:38 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-26 20:38 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-97985
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: af_unix: Update last skb marker in manage_oob(). [ Upstream
Commit: 0630bfc773d85ac44da05b2c5a037dbbd39301ab
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0630bfc773d85ac44da05b2c5a037dbbd39301ab
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97985
Analysis date: Sat, 26 Sep 2026 16:38:02 -0400
ActionableScore: 2
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-2026-97985 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97985
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-2026-97985 LOW https://www.kernelcve.org/list/?q=CVE-2026-97985 CHECK WITH IMPACT FROM ORIG NN MODERATE 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-835;**CWE-400;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'A logic error in AF_UNIX OOB handling can leave the last skb marker stale after manage_oob skips or unlinks an OOB skb. A blocking recv(MSG_PEEK) with no copied data can then call unix_stream_data_wait, return immediately, and repeat without sleeping, causing a CPU busy loop. For the CVSS the PR:L value is used because any local unprivileged process able to create and use an AF_UNIX SOCK_STREAM socket can trigger the condition without special capabilities. The issue is not network reachable because AF_UNIX sockets provide local IPC rather than remote network transport. The realistic impact is limited CPU denial of service, while sustained triggering by multiple threads may cause broader system availability degradation. There is no memory corruption primitive, information disclosure, or plausible privilege escalation path in the affected code.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) SKIP CVE-2026-97985 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE REMOTE OOB LOCK DANGER SKB HARDWARE DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=2
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 2
* Paranoid score: 2
* No floor or cap applied.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 Local unprivileged trigger. An ordinary process can create an AF_UNIX SOCK_STREAM socket pair and issue the required MSG_OOB and MSG_PEEK operations without capabilities.
* +1 Strong local DoS. The stale progress marker causes a deterministic busy-wait that can consume a CPU, and multiple attacker-created workers can increase CPU pressure.
* No extra Availability point. Repeating the same busy loop across threads is not an independent consequence.
* No memory-corruption signal. The stale `last` value is a logical wait marker, not a dangling object reference.
* No UAF, OOB access, repeated release, disclosure, arbitrary write, authorization bypass, or privilege-escalation primitive is established.
* No remote-reachability point. AF_UNIX is local IPC.
* No race penalty. The trigger is an ordered and inexpensive socket operation sequence, not a narrow timing race.
* No resource-leak signal. The patch fixes CPU spinning rather than a permanently lost kernel reference.
3. Reachability analysis
Any ordinary local user can instantiate the required socket pair and drive the complete trigger using `send()` and `recv()`. No capability, namespace privilege, host-administrator action, prior privileged setup, special hardware, or externally controlled network traffic is required. The affected path requires AF_UNIX OOB support in the kernel, but the attacker does not need to configure or enable it at runtime. Triggering is deterministic and repeatable rather than race-dependent.
4. Primitive and severity interpretation
The defect is a control-flow and wait-state bookkeeping error. `manage_oob()` advances past or unlinks an OOB skb without updating the `last` marker used by `unix_stream_data_wait()`. The wait function therefore incorrectly concludes that queue state changed and returns immediately, causing repeated execution without sleeping.
No skb is shown to be accessed after its lifetime, and no memory ownership or refcount invariant is violated. This is therefore `PrimitiveClass=NONE`, not a Class B UAF or Class C invalid dereference. The demonstrated consequence is local CPU consumption. Broader availability degradation through many busy-waiting threads is plausible but remains the same resource-exhaustion mechanism, not an additional paranoid primitive.
`ImportantCandidate=NO` because there is no corruption, security-boundary bypass, persistent cross-owner effect, or leverage beyond CPU denial of service. `AutoDowngradeAllowed=YES` because no unresolved security primitive would be lost by treating this as an ordinary availability issue.
5. One-sentence report phrase
A local unprivileged process can trigger an AF_UNIX MSG_PEEK busy loop through stale receive-queue progress tracking, causing CPU denial of service without memory corruption or privilege escalation.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The patch and surrounding control flow establish a deterministic CPU-spin bug with no lifetime, corruption, disclosure, authorization, or privilege-escalation primitive.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: af_unix: Update last skb marker in manage_oob(). [ Upstream
Commit: 0630bfc773d85ac44da05b2c5a037dbbd39301ab
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0630bfc773d85ac44da05b2c5a037dbbd39301ab
Changed files:
net/unix/af_unix.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=0630bfc773d85ac44da05b2c5a037dbbd39301ab
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97985 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97985
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:L/UI:N/S:U/C:N/I:N/A:L
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: 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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