[CVE-2026-64174][MODERATE 7.0] wifi: cfg80211: advance loop vars in cfg80211_merge_profile()

[CVE-2026-64174][MODERATE 7.0] wifi: cfg80211: advance loop vars in cfg80211_merge_profile()

[AL-KERNEL]

CVE: CVE-2026-64174
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: wifi: cfg80211: advance loop vars in cfg80211_merge_profile()
Commit: 5817e1e5205498a5df66eba2b34e817f4210fd0f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5817e1e5205498a5df66eba2b34e817f4210fd0f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64174
Analysis date: Sun, 19 Jul 2026 15:49:52 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: NO

Summary:
A crafted WiFi beacon can cause `cfg80211_merge_profile()` to repeatedly process the same Multi-BSSID continuation data, leading to excessive CPU time in the kernel wireless parsing path and potential adjacent-network denial of service.

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

The original Linux kernel CVE announcement for CVE-2026-64174 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64174

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: NO

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
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CVE-2026-64174	MODERATE	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:N/I:N/A:H';CWE-834;**CWE-400;*CWE-835;Other CVSS 'AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '6.5';DESCR 'cfg80211_merge_profile can repeatedly process the same Multi-BSSID continuation data because mbssid_elem and sub_elem are not advanced after a continuation is consumed. A malicious access point or frame injector within wireless range can send crafted beacon frames that make the kernel spend excessive CPU time in this parsing path, reportedly up to about 2ms per beacon. For the CVSS the PR:N is used because no local account is required and the attacker only needs adjacent wireless reachability to the victim radio. The vector is AV:A rather than AV:N because the trigger requires local radio proximity or access to the same wireless medium. Impact is denial of service or performance degradation only. There is no supported confidentiality or integrity impact because the patch shows repeated iteration and bounded copying rather than UAF, OOB write, or another memory corruption primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	REMOTE KPANIC 	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Remote or adjacent network trigger: +2
  Crafted beacon frames can be sent by a malicious AP or frame injector within WiFi range. This is not Internet remote, but it is externally triggerable without a local account.
* Availability impact realistic: +1
  The commit states up to about 2ms CPU time per beacon in `cfg80211_merge_profile()`, so repeated malicious beacons can cause measurable CPU degradation.
* Broad/common subsystem exposure: +1
  `cfg80211` beacon parsing is a common WiFi client path on systems with wireless enabled.

Paranoid additional signal:

* Reliable kernel CPU DoS concern: +1
  If malicious beacons are sent at scale or across multiple radios, the repeated parsing cost could become a practical local-radio DoS.

Not counted:

* No generic memory corruption. The repeated `memcpy()` appears bounded by the destination buffer accounting.
* No UAF, OOB write, type confusion, refcount misuse, or stale callback primitive is shown.
* No confidentiality or integrity impact is supported by the patch.

## 3. Reachability analysis

The trigger is a crafted WiFi beacon processed by the victim wireless stack during scanning or beacon handling. The attacker does not need a local user account, but does need adjacent wireless reachability or control of a nearby AP or transmitter. Namespaces and containers are not the main factor because the input arrives through the physical wireless medium. The path is relevant on systems with WiFi enabled and scanning active. It is not reachable over normal routed IP networking.

## 4. Severity interpretation

This behaves more like an actionable Moderate than an Important vulnerability. The issue is externally triggerable over the adjacent wireless medium with PR:N, which makes it unsuitable for automatic low-priority closure. However, the demonstrated impact is CPU consumption and availability degradation only. There is no evidence of memory corruption, privilege escalation, information disclosure, or persistent system compromise.

## 5. One-sentence report phrase

A crafted WiFi beacon can cause `cfg80211_merge_profile()` to repeatedly process the same Multi-BSSID continuation data, leading to excessive CPU time in the kernel wireless parsing path and potential adjacent-network denial of service.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: the bug is PR:N and externally triggerable from the adjacent wireless medium, but the patch supports DoS-only impact with no demonstrated memory corruption or privilege escalation primitive.

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

Patch: wifi: cfg80211: advance loop vars in cfg80211_merge_profile()
Commit: 5817e1e5205498a5df66eba2b34e817f4210fd0f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5817e1e5205498a5df66eba2b34e817f4210fd0f

Commit description:

cfg80211_merge_profile() reassembles a Multi-BSSID non-transmitted BSS
profile that has been split across multiple consecutive MBSSID elements.
Its while-loop calls

	cfg80211_get_profile_continuation(ie, ielen, mbssid_elem, sub_elem)

but never advances mbssid_elem or sub_elem inside the body.  Each
iteration therefore searches for a continuation that follows the same
fixed pair; the helper returns the same next_mbssid; and the same
next_sub bytes are memcpy()'d into merged_ie at a growing offset until
the buffer fills.

Advance both mbssid_elem and sub_elem to the just-consumed continuation
so the next call to cfg80211_get_profile_continuation() searches for a
further continuation beyond it (or returns NULL when none exists).

A specially-crafted malicious beacon can take advantage of this bug
to cause the kernel to spend an excessive amount of time in
cfg80211_merge_profile (up to as much as 2ms per beacon received),
which could theoretically be abused in some way.

Cc: stable@vger.kernel.org
Fixes: fe806e4 ("cfg80211: support profile split between elements")
Signed-off-by: John Walker <johnwalker0@gmail.com>
Link: https://patch.msgid.link/20260507230720.64783-1-johnwalker0@gmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/wireless/scan.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=5817e1e5205498a5df66eba2b34e817f4210fd0f

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

The original Linux kernel CVE announcement for CVE-2026-64174 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64174

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:L/PR:N/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 6.5

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: 4
  Paranoid ActionableScore: 5

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