* [CVE-2026-98699][MODERATE 7.0] wifi: mac80211: fix mesh fast xmit path deletion UAF
@ 2026-10-24 10:17 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-24 10:17 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98699
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: wifi: mac80211: fix mesh fast xmit path deletion UAF
Commit: 0117f1aa189495e6f1ff608681678817995aee39
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0117f1aa189495e6f1ff608681678817995aee39
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98699
Analysis date: Sat, 24 Oct 2026 06:17:47 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES
Summary:
A mesh peer can race path deletion against fast-transmit cache insertion, leaving a freed `mesh_path` pointer available to later kernel transmit processing.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98699 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98699
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-2026-98699 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98699 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=4 LEGACY=MODERATE_KPANIC RESULT=SAME (final reconciliation agrees; DECISION: both MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;*CWE-672;Other CVSS 'AV:A/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.5';DESCR 'A race in mac80211 mesh fast transmit caching can insert a raw mesh_path pointer after path deletion already flushed the cache. The path is later released with kfree_rcu, leaving a cache entry that can dereference freed memory during a subsequent transmit. An attacker must be within radio range and able to induce mesh path deletion with concurrent traffic, so AV:A and AC:H are appropriate. For the CVSS the PR:L base value reflects a secured mesh where a peer needs mesh credentials. The paranoid vector uses PR:N for an open or otherwise joinable mesh and uses HHH because reclaim of the freed path could turn the stale pointer into broader kernel memory corruption, although no reliable write primitive is proven. Automated impact decision path. The original SimpleNet classifier selected IMPORTANT. The primary LLM estimated paranoid CVSS 7.5 and the production ActionableScore returned 6 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were KP and FD specialist checks stage IMPORTANT to MODERATE_KPANIC because KP specialist did not establish a qualifying panic. 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 DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP. The independent weaker Aegis shadow evaluated CVSS 3.1 and ActionableScore 4 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 6) MAYBE REMOTE LOCK UAF KPANIC DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=6
ActionableScoreLower=5
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: 5.
* Conservative score: 5; no floor or cap changed the arithmetic.
* Raw paranoid score: 6.
* Paranoid score: 6; includes one point for defensible active structured-object consumption.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
* +2 Real UAF: deletion flushes the cache and schedules `mesh_path` through `kfree_rcu()`, while an in-flight lookup can republish the same raw pointer after the flush.
* +2 network-peer reachability: supplied evidence grounds a radio-range mesh peer inducing path deletion while traffic drives cache insertion/use.
* +1 plausible kernel crash/DoS from subsequent transmit dereferencing the freed path.
* +1 attacker-influenced lifetime sequence: the peer can induce deletion and concurrent traffic, materially affecting the vulnerable race.
* -1 hard timing: insertion must occur after cache flush but before deletion becomes visible; supplied evidence explicitly assesses AC:H.
* Paranoid +1 structured stale-object leverage: the stale `mesh_path`/MPP path is retained for later fast-transmit processing, not merely cleanup. Exact fields and reuse contents are not shown.
No controlled reclaim, arbitrary write, callback control, disclosure, or LPE is demonstrated. Confidentiality and integrity bonuses are therefore withheld. The same crash is not counted again as Availability.
3. Reachability analysis
The evidenced attacker is an adjacent wireless mesh peer, potentially requiring mesh credentials on secured deployments but not host UID 0 or host-administrator capability. An existing mesh interface is a deployment prerequisite. No namespace capability participates. Repeated traffic and path changes make retrying possible, although winning the specific race is assessed as difficult.
4. Primitive and severity reading
This is an active structured-object RCU UAF: a raw `mesh_path` pointer can escape the deletion flush, survive in the fast-transmit cache, and be consumed after `kfree_rcu()`. It is broader than a cleanup-only stale dereference, but no attacker-shaped reclaim or directed corruption establishes CLASS_A.
The wireless-peer-to-kernel boundary and later privileged transmit consumer leave material exploit leverage unknown. Thus `ImportantCandidate=YES` and automatic downgrade is unsafe, without claiming proven Important severity or C/I impact. There is no authorization decision bypass; B4-PENDING does not apply.
5. One-sentence report phrase
A mesh peer can race path deletion against fast-transmit cache insertion, leaving a freed `mesh_path` pointer available to later kernel transmit processing.
6. Manual review advice
MANUAL CHECK REQUIRED
Review the later fast-transmit field consumers, allocator reuse opportunities, and practical mesh-peer control over repeated deletion races.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: wifi: mac80211: fix mesh fast xmit path deletion UAF
Commit: 0117f1aa189495e6f1ff608681678817995aee39
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0117f1aa189495e6f1ff608681678817995aee39
Commit description:
mesh_fast_tx_cache() stores raw mesh_path pointers. Path deletion
flushes the cache and then frees the path with kfree_rcu(), but a
lookup that already holds the path can insert a new cache entry
after the flush. The cache then points at freed memory.
Set MESH_PATH_DELETED before flushing, and skip inserting a cache
entry if the path or MPP path is already deleted. Check this under
the cache walk lock so it is ordered with the flush. Use WRITE_ONCE()
for the deletion flag updates because the cache check reads flags
without taking state_lock.
Fixes: d5edb9a ("wifi: mac80211: mesh fast xmit support")
Cc: [email protected]
Reported-by: Vega <[email protected]>
Assisted-by: LLM
Co-developed-by: Luxing Yin <[email protected]>
Signed-off-by: Luxing Yin <[email protected]>
Signed-off-by: Zihan Xi <[email protected]>
Link: https://patch.msgid.link/1daa7a98199fe6965c2da7c42717073a6fd39a0b.1789615568.git.zihanx@nebusec.ai
Signed-off-by: Johannes Berg <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
net/mac80211/mesh_pathtbl.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=0117f1aa189495e6f1ff608681678817995aee39
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98699 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98699
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:A/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
The Best / paranoid CVSS score: 7.5
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: 5
Paranoid ActionableScore: 6
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).
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