* [CVE-2026-99211][MODERATE 7.0] netlink: reset skb headers before unicast and multicast filtering [ Upstream
@ 2026-10-30 15:32 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-10-30 15:32 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-99211
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: netlink: reset skb headers before unicast and multicast filtering [ Upstream
Commit: 06791594274f87c29f1a9f1961d700272716a49d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=06791594274f87c29f1a9f1961d700272716a49d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99211
Analysis date: Fri, 30 Oct 2026 11:32:34 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline / manual review recommended
Manual review required: YES
Summary:
An unprivileged NETLINK_RDMA socket filter can use stale skb header offsets to infer kernel skb-headroom contents through reply delivery or length.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99211 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99211
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: MODERATE 7.0
Manual review required: YES
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-99211 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-99211 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=3 LEGACY=MODERATE_KPANIC RESULT=SAME V39_AEGIS_ONE_STEP_UP=MODERATE->MODERATE_KPANIC (final reconciliation agrees; DECISION: both MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N';*CWE-200;CWE-908;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '5.5';DESCR 'This is an uninitialized kernel memory disclosure rather than memory corruption. A local NETLINK_RDMA user can attach a classic socket filter that reads relative to stale network or MAC header offsets and can encode observations into whether the reply is delivered or into its returned length. For the CVSS the PR:L value is selected because an attacker needs a local user context and control of a netlink socket, but no administrative capability is indicated for the demonstrated IWPM path. AC:L is appropriate because the demonstrated primitive does not depend on a race. The base confidentiality impact is limited because the observable region is skb headroom and the channel is indirect. The paranoid score uses C:H only as an upper bound if repeated filtering queries permit systematic recovery of sensitive stale kernel data. There is no supported write primitive, privilege escalation path, direct network trigger, or availability impact. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 5.5 and the production ActionableScore returned 4 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage LOW to MODERATE_KPANIC because the manual review requirement was applied. KP and FD specialist checks stage MODERATE_KPANIC to MODERATE because KP specialist did not establish a qualifying panic. final reconciliation stage MODERATE to MODERATE_KPANIC because the cross model evidence reconciliation rule was applied. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK and DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 3.3 and ActionableScore 3 with primitive class NONE and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4) MAYBE SIMPLEFIX LEAK SKB INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP KPANIC V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=4
ActionableScoreLower=3
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: 3.
* Conservative score: 3; no floor or cap applied.
* Raw paranoid score: 4.
* Paranoid score: 4; adds broader exposure through the shared netlink unicast/broadcast filtering paths.
* Final recommended bucket: **Borderline / manual review recommended**::
2. Signal breakdown
* +1 Local unprivileged trigger: the commit explicitly identifies an unprivileged NETLINK_RDMA user attaching a classic socket filter.
* +1 High-control local API: the attacker controls filter-relative reads and predicates, allowing selected headroom observations to affect reply delivery or length.
* +1 Confidentiality plausible: stale network/MAC header offsets let the filter inspect initialized-allocation headroom preceding the netlink message, with an observable length/delivery channel.
* Paranoid +1 Broad path exposure: the fix changes central netlink unicast and broadcast filter sites and explicitly covers other producers, though only IWPM is concretely demonstrated.
* No write, UAF, authorization bypass, crash, arbitrary read, LPE, or direct remote reachability is shown.
* C:H is not awarded: the observable area is constrained skb headroom, and systematic recovery of sensitive data is not established.
3. Reachability analysis
The evidenced trigger is a local, non-UID-0 NETLINK_RDMA socket user; no administrative capability or namespace-scoped privilege is indicated. The attacker can attach a classic socket filter and exercise the IWPM reply path without a race. No prior host setup, special hardware requirement, or remote packet path is demonstrated.
4. Primitive and severity reading
The primitive is a bounded, read-only disclosure of previously initialized kernel allocation contents through stale skb header offsets and an indirect filter oracle. It is CLASS_B rather than memory corruption or a major CLASS_A disclosure. The patch resets both offsets immediately before privileged kernel filter execution. Important-grade sensitive-data recovery remains unproven, so this is not an Important candidate and may be downgraded after review.
5. One-sentence report phrase
An unprivileged NETLINK_RDMA socket filter can use stale skb header offsets to infer kernel skb-headroom contents through reply delivery or length.
6. Manual review advice
MANUAL CHECK RECOMMENDED
Confirm the maximum observable headroom, query repeatability, and whether sensitive allocator contents can realistically be reconstructed.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: netlink: reset skb headers before unicast and multicast filtering [ Upstream
Commit: 06791594274f87c29f1a9f1961d700272716a49d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=06791594274f87c29f1a9f1961d700272716a49d
Changed files:
net/netlink/af_netlink.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=06791594274f87c29f1a9f1961d700272716a49d
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99211 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99211
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:L/I:N/A:N
The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
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: 3
Paranoid ActionableScore: 4
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: MODERATE
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): MODERATE 7.0
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).
^ permalink raw reply [relevance 21%]
Results 1-1 of 1 | reverse | sort options + mbox downloads above
-- links below jump to the message on this page --
2026-10-30 15:32 21% [CVE-2026-99211][MODERATE 7.0] netlink: reset skb headers before unicast and multicast filtering [ Upstream AL-KERNEL
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox