[CVE-2026-72003][IMPORTANT] wifi: brcmfmac: cyw: fix heap overflow on a short auth frame

[CVE-2026-72003][IMPORTANT] wifi: brcmfmac: cyw: fix heap overflow on a short auth frame

[AL-KERNEL]

CVE: CVE-2026-72003
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: wifi: brcmfmac: cyw: fix heap overflow on a short auth frame
Commit: 55b26abb1fa1ec406b3ad11b43c49c7624257565
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=55b26abb1fa1ec406b3ad11b43c49c7624257565
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72003
Analysis date: Sat, 15 Aug 2026 03:02:11 -0400
ActionableScore: 9
ActionableScore lower bound: 7
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A malicious AP can send a short external SAE authentication frame that causes unsigned length underflow in brcmfmac cyw and triggers an adjacent-network kernel heap overflow, leading to DoS and possible kernel memory corruption.

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

The original Linux kernel CVE announcement for CVE-2026-72003 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72003

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: IMPORTANT
Manual review required: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-72003	IMPORTANT	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H';CWE-122;*CWE-787;CWE-191;*CWE-20;BEST CVSS score: '8.8';DESCR 'A heap overflow in brcmfmac cyw external SAE authentication handling can occur because brcmf_notify_auth_frame_rx() subtracts the IEEE 802.11 management header offset from a too small unsigned frame length. A malicious or malfunctioning AP can provide a short auth frame so the subtraction wraps to a very large copy length and memcpy writes past the allocated management frame buffer. For the CVSS the PR:N is selected because the attacker does not need privileges on the victim system and only needs the ability to interact with the victim over the adjacent Wi-Fi link. The issue is adjacent network reachable rather than Internet reachable because exploitation requires radio proximity or control of an AP used by the station. Impact can include kernel memory corruption, denial of service, and potentially privilege escalation or code execution in the kernel due to the heap overflow primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 9)	YES	REMOTE SIMPLEFIX NETWORK KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS	YES	NO	checked

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

ActionableScore=9
ActionableScoreLower=7

## 1. ActionableScore

* Conservative score: 7
* Paranoid score: 9
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Remote reachable / network-triggerable: +2. A malicious AP can trigger the vulnerable path over Wi-Fi during external SAE authentication. This is adjacent-network reachable, not Internet-routable.
* Memory corruption, strong corruption primitive: +2. The unsigned subtraction can wrap and cause memcpy() to write far past a kzalloc() buffer.
* Weak LPE concern: +1. Kernel heap overflow makes privilege escalation plausible, but the patch does not demonstrate target selection, reclaim control, or a reliable overwrite target.
* Reliable kernel crash / strong DoS: +1. A large out-of-bounds memcpy in kernel heap is a realistic crash vector.
* Privileged kernel/device-management memory corruption path: +1. The corruption is in a trusted wireless driver path fed by firmware/AP-originated management frame data.
* Confidentiality impact plausible: +1. Kernel heap corruption can plausibly lead to disclosure in worst practical analysis.
* Integrity impact plausible: +1. Kernel heap overwrite can plausibly corrupt kernel state.
* Corruption primitive constrained or payload/target not fully controlled: -1. The oversized copy source is derived from the received/firmware event buffer and surrounding memory, not clearly an arbitrary attacker-chosen payload.
* Specific hardware/protocol mode dependency: -1. Requires affected brcmfmac/cyw hardware and the external SAE authentication path.

Paranoid adjustment:

* Privilege escalation plausibility upgraded from weak +1 to strong +2 because this is a remotely influenced kernel heap OOB write primitive.
* The specific-mode penalty is dropped in the paranoid score because Wi-Fi client authentication paths are realistic on affected devices.

## 3. Reachability analysis

The attacker does not need local code execution or credentials on the victim. The realistic attacker is a malicious or malfunctioning AP, or an attacker able to influence the AP/authentication exchange within Wi-Fi range. This is best treated as adjacent-network reachable rather than AV:N Internet reachable. Containers and namespaces are not relevant because triggering is external to the local userspace privilege model. The path is hardware and driver dependent, and requires the affected brcmfmac cyw external SAE authentication support to be in use.

Call-site confidence: high. The patch and commit directly show the vulnerable length arithmetic and the memcpy() sink.

## 4. Severity interpretation

This is not an ordinary Moderate DoS-only bug. The demonstrated primitive is a kernel heap overflow caused by unsigned length underflow before memcpy(). Realistic exploitation may be constrained by firmware behavior, heap layout, and kernel hardening, but the bug class and adjacent remote trigger justify Important-level manual handling. The conservative interpretation is Strong Important candidate. The paranoid interpretation reaches high-end Important because kernel heap OOB write can potentially support privilege escalation or code execution if the overwrite becomes controllable.

## 5. One-sentence report phrase

A malicious AP can send a short external SAE authentication frame that causes unsigned length underflow in brcmfmac cyw and triggers an adjacent-network kernel heap overflow, leading to DoS and possible kernel memory corruption.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the patch fixes a remotely influenced kernel heap overflow in a wireless driver path, with plausible confidentiality, integrity, and availability impact beyond a simple crash.

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

Patch: wifi: brcmfmac: cyw: fix heap overflow on a short auth frame
Commit: 55b26abb1fa1ec406b3ad11b43c49c7624257565
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=55b26abb1fa1ec406b3ad11b43c49c7624257565

Commit description:

brcmf_notify_auth_frame_rx() takes the frame length from the firmware
event and copies the frame body with the management header offset
subtracted:

	u32 mgmt_frame_len = e->datalen - sizeof(struct brcmf_rx_mgmt_data);
	...
	memcpy(&mgmt_frame->u, frame,
	       mgmt_frame_len - offsetof(struct ieee80211_mgmt, u));

The only length check is e->datalen >= sizeof(*rxframe), so mgmt_frame_len
can be anything from 0 up. offsetof(struct ieee80211_mgmt, u) is 24. When
mgmt_frame_len is below that, the subtraction wraps as an unsigned value to
a huge length. The memcpy then runs far past the kzalloc'd buffer. A
malicious or malfunctioning AP can make the frame short during the
external SAE auth exchange, so this is a remotely triggered heap overflow.

Reject frames shorter than the management header offset before the copy.

Fixes: 66f9093 ("wifi: brcmfmac: cyw: support external SAE authentication in station mode")
Link: https://lore.kernel.org/r/178214417708.2368577.16740907093694208834@maoyixie.com
Cc: stable@vger.kernel.org
Co-developed-by: Kaixuan Li <kaixuan.li@ntu.edu.sg>
Signed-off-by: Kaixuan Li <kaixuan.li@ntu.edu.sg>
Signed-off-by: Maoyi Xie <maoyixie.tju@gmail.com>
Acked-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Link: https://patch.msgid.link/20260627131313.3878893-1-maoyixie.tju@gmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/net/wireless/broadcom/brcm80211/brcmfmac/cyw/core.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=55b26abb1fa1ec406b3ad11b43c49c7624257565

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

The original Linux kernel CVE announcement for CVE-2026-72003 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72003

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: Not available
  The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 8.8

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: 7
  Paranoid ActionableScore: 9

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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

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).