* [CVE-2026-98394][LOW] af_unix: Return immediately when manage_oob() returns NULL for 0-length buffer. [ Upstream
@ 2026-10-15 2:06 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-10-15 2:06 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98394
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: af_unix: Return immediately when manage_oob() returns NULL for 0-length buffer. [ Upstream
Commit: 3d3c7a3df66b2ca3d2cd1a2a0c37eb701feba713
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3d3c7a3df66b2ca3d2cd1a2a0c37eb701feba713
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98394
Analysis date: Wed, 14 Oct 2026 22:06:57 -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-2026-98394 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98394
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-2026-98394 LOW https://www.kernelcve.org/list/?q=CVE-2026-98394 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT LOW AEGIS_AS=1 LEGACY=LOW RESULT=SAME (legacy and Aegis reconciliation agree; DECISION: both LOW) 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 unix_stream_read_generic() can cause a blocking recv(0, MSG_PEEK) call to busy wait when the last queued AF_UNIX skb contains OOB data. manage_oob() returns NULL in this state, but the old exit condition does not stop the loop when both copied and the requested buffer size are zero. For the CVSS the PR:L value is used because a local user or process must create or access an AF_UNIX socket and arrange the required OOB queue state. The issue is not remotely network reachable and does not expose a memory corruption primitive. Impact is limited to availability through a stuck calling thread and CPU consumption. Sustained parallel triggering could increase resource pressure, but a kernel crash, information disclosure, integrity violation, or privilege escalation is not supported by the affected code path. Automated impact decision path. The original SimpleNet classifier selected IMPORTANT. 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 IMPORTANT to MODERATE_KPANIC because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE_KPANIC to LOW because the ActionableScore threshold rule was applied. final reconciliation stage LOW to LOW because KP specialist did not establish a qualifying panic. 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 LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS and DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 and KPANIC_UNSUPPORTED_REMOVED. The independent weaker Aegis shadow evaluated CVSS 3.3 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 2) MAYBE REMOTE OOB LOCK DANGER SIMPLEFIX SKB LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 KPANIC_UNSUPPORTED_REMOVED - - guess
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=2
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 2
* Paranoid score: 2
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 Local unprivileged trigger. An ordinary local process can create an AF_UNIX stream socket, queue OOB data, and invoke blocking `recv(0, MSG_PEEK)` without administrative privileges.
* +1 Availability impact. The affected call can busy-wait in kernel context, consuming CPU and leaving the calling thread stuck until interrupted.
* No UAF, OOB access, heap corruption, stale lifetime operation, write primitive, or information disclosure is established.
* No strong DoS point was awarded because a kernel panic, host-wide lockup, or persistent resource exhaustion is not demonstrated.
* No additional resource-exhaustion point was awarded. Parallel triggering can increase CPU pressure, but it provides no demonstrated isolation bypass and is broadly comparable to an unprivileged process consuming its available CPU quota.
* No remote-reachability point was awarded because AF_UNIX is local IPC.
* NEW52 B5-R does not apply because there is no heap OOB write, retry-accumulated offset, or later consumption of corrupted state.
* NEW53 B3-PENDING does not apply because no shared-backing or file-backed write occurs.
* NEW54 B4-PENDING does not apply because no authorization decision or mandatory security guard is bypassed.
3. Reachability analysis
The complete trigger is available to an ordinary local user through AF_UNIX socket operations. The attacker can create the socket endpoints, place an MSG_OOB skb at the end of the receive queue, and issue a zero-length blocking receive with MSG_PEEK.
No UID 0, capability, namespace privilege, prior administrator setup, special hardware, sysctl, or boot option is required beyond a kernel built with AF_UNIX OOB support. This is not a race. The required queue state and receive arguments can be arranged deterministically. The effect is local and is not reachable through TCP or other remote network traffic.
4. Primitive and severity interpretation
The exact defect is a loop-termination logic error. `manage_oob()` can return NULL while both `copied` and `state->size` are zero, but the old condition does not break from `unix_stream_read_generic()`. The result is a kernel-side busy-wait rather than immediate return of zero.
There is no stale object, post-lifetime access, repeated release, memory corruption, authorization bypass, or shared-storage ownership violation. The appropriate classification is CLASS_C because the demonstrated behavior is availability-only invalid control flow.
The practical consequence is a stuck calling thread and CPU consumption. Broader CPU pressure from multiple callers is possible, but no host crash, persistent exhaustion, confidentiality impact, integrity impact, or privilege escalation is supported. ImportantCandidate is therefore NO, and automatic downgrade is safe.
5. One-sentence report phrase
A local unprivileged process can make a zero-length blocking AF_UNIX receive with MSG_PEEK busy-wait when the final queued skb contains OOB data, causing limited CPU consumption without memory corruption or privilege escalation.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The patch establishes a deterministic local busy-wait with no corruption, lifetime, authorization, cross-boundary, or persistent resource-leak primitive.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: af_unix: Return immediately when manage_oob() returns NULL for 0-length buffer. [ Upstream
Commit: 3d3c7a3df66b2ca3d2cd1a2a0c37eb701feba713
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3d3c7a3df66b2ca3d2cd1a2a0c37eb701feba713
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=3d3c7a3df66b2ca3d2cd1a2a0c37eb701feba713
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98394 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98394
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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