[CVE-2026-63869][LOW] wifi: mac80211: limit injected antenna index in ieee80211_parse_tx_radiotap [ Upstream

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-63869
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: wifi: mac80211: limit injected antenna index in ieee80211_parse_tx_radiotap [ Upstream
Commit: f6d3dc8e8492bf8435e0b23c99472af7bafd6b44
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f6d3dc8e8492bf8435e0b23c99472af7bafd6b44
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63869
Analysis date: Sun, 19 Jul 2026 11:32:16 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A local user with frame injection capability can supply an invalid radiotap antenna index that causes a shift-out-of-bounds condition in mac80211, resulting mainly in UBSAN warning or local DoS on hardened kernels.

======================================================================
ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-63869 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63869

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-2026-63869	LOW	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:L/UI:N/S:U/C:N/I:N/A:H';CWE-1335;*CWE-20;CWE-682;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 shift out of bounds bug in mac80211 radiotap parsing occurs because ieee80211_parse_tx_radiotap uses the userspace supplied IEEE80211_RADIOTAP_ANTENNA value directly as the BIT shift count. An attacker who can inject frames through a local monitor interface can provide an antenna index larger than the 2 bit control.antennas bitmap can represent, which triggers undefined behavior and UBSAN reports. For the CVSS the PR:L is used because reliable triggering requires local ability to send injected monitor frames or access a prepared monitor interface, but does not necessarily require full administrative control in all deployments. The issue is not network reachable through normal WiFi traffic and is a local control path issue. Impact is denial of service or warning based failure only, with no supported evidence of memory corruption, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES	REMOTE WRITE KASAN OOB SYZBOT PACKET  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	YES	NO	checked

======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Conservative signals:

* Availability impact realistic: +1. The bug is a userspace-controlled shift-out-of-bounds detected by UBSAN and may cause warning-based failure in hardened/debug kernels.
* No generic memory corruption: +0. The patch shows an invalid shift count in BIT(), not an OOB write, UAF, double free, type confusion, stale pointer, refcount bug, or arbitrary write.
* No confidentiality or integrity impact: +0. There is no read-back path, disclosure primitive, overwrite primitive, or privilege boundary bypass.
* Not remote reachable: +0. The path is monitor-mode frame injection from local userspace, not normal received WiFi traffic.
* Special/local capability-dependent path: effectively keeps the score low. Triggering normally requires access to packet injection through a monitor interface and often CAP_NET_RAW or CAP_NET_ADMIN setup.

Paranoid additional signal:

* Reliable kernel crash / strong DoS: +1. In configurations where UBSAN, panic_on_warn, or similar hardening treats the shift-out-of-bounds report as fatal, this can become a stronger local DoS.

## 3. Reachability analysis

The bug is triggered by a locally supplied radiotap header on the mac80211 injection transmit path. A remote WiFi peer cannot normally trigger this through ordinary packet reception. Practical triggering requires a local process able to inject frames through a monitor interface. In typical deployments, creating or configuring such an interface requires elevated network privileges, while sending may require CAP_NET_RAW or access to an already prepared monitor interface. Network namespaces may reduce the practical privilege requirement if a container or sandbox is delegated the relevant wireless or raw packet capabilities, but this is not a default broad unprivileged interface.

Call-site confidence: high. The commit includes the relevant call trace through ieee80211_monitor_start_xmit() and packet_sendmsg().

## 4. Severity interpretation

This behaves like an ordinary Low or lower-end Moderate issue rather than an Important-class vulnerability. The theoretical concern is undefined behavior from an out-of-range shift, but the patch and context do not support a concrete memory corruption primitive, object lifetime issue, information leak, or privilege escalation path. Realistic impact is local DoS or warning-based failure in affected debug or hardened configurations.

## 5. One-sentence report phrase

A local user with frame injection capability can supply an invalid radiotap antenna index that causes a shift-out-of-bounds condition in mac80211, resulting mainly in UBSAN warning or local DoS on hardened kernels.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is a validation fix for a bounded antenna index in a local injection path, with no supported memory corruption or privilege escalation primitive.

======================================================================
UPSTREAM PATCH SUMMARY
======================================================================

Patch: wifi: mac80211: limit injected antenna index in ieee80211_parse_tx_radiotap [ Upstream
Commit: f6d3dc8e8492bf8435e0b23c99472af7bafd6b44
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f6d3dc8e8492bf8435e0b23c99472af7bafd6b44

Changed files:
  net/mac80211/tx.c
  net/packet/af_packet.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=f6d3dc8e8492bf8435e0b23c99472af7bafd6b44

======================================================================
DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-63869 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63869

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: 1
  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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).