* [CVE-2026-93792][MODERATE REGULAR] wifi: iwlwifi: mvm: fix a possible underflow [ Upstream
@ 2026-09-24 21:53 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-24 21:53 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-93792
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: wifi: iwlwifi: mvm: fix a possible underflow [ Upstream
Commit: 38ad8339211bf24c19126ec7629ea52094676454
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=38ad8339211bf24c19126ec7629ea52094676454
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93792
Analysis date: Thu, 24 Sep 2026 17:53:55 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline / manual review recommended
Manual review required: YES
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-93792 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93792
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 REGULAR
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-2026-93792 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-93792 CHECK WITH IMPACT FROM ORIG NN MODERATE 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-191;*CWE-787;CWE-125;CWE-191;*CWE-787;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.5';DESCR 'An integer underflow can occur in the iwlwifi WoWLAN wakeup packet parser when firmware reports a packet length that is too small for the calculated 80211 header IV and ICV lengths. A nearby WiFi attacker may be able to influence the packet delivered through the firmware wakeup path, although practical triggering depends on WoWLAN configuration firmware behavior and a specific malformed frame state. For the CVSS the PR:N is used because the attacker does not need a local account on the target. The attack vector is adjacent AV:A rather than network AV:N because the input is received over the WiFi radio path. Impact is at least denial of service and may include limited confidentiality or integrity impact if the length underflow reaches an unsafe skb copy or buffer access. The paranoid score uses C:H I:H A:H as a manual review boundary because this is a kernel memory handling bug with a possible corruption primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) YES REMOTE OOB SIMPLEFIX NETWORK SKB PACKET INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=3
ActionableScoreLower=2
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 3
* Paranoid score: 3
* Final recommended bucket: **Borderline / manual review recommended**::
No score floor or cap was applied.
2. Signal breakdown
Positive signals:
* +1 Constrained kernel memory-corruption candidate. The patch establishes that firmware-supplied `pktsize` was insufficiently validated before `hdrlen`, `ivlen`, and `icvlen` were subtracted and before data was copied into an skb. A negative or underflowed length can reach skb handling and may result in an out-of-bounds read or skb buffer overwrite. The exact later copy/use sites are not included in the supplied context.
* +1 Firmware-mediated external influence. The vulnerable length originates from a WoWLAN wakeup packet report received from WiFi firmware. Firmware mediation is material, and a nearby wireless actor may influence packet contents reaching that reporting path, but this is not established as a direct reliable attacker-controlled trigger in the supplied patch.
* +1 Paranoid only. The packet header controls `hdrlen`, while firmware provides `pktsize`. The mismatch can make the invalid length attacker-relevant if malformed 802.11 frames can cause inconsistent firmware wake reports. This remains unresolved and is not treated as proof of controlled overwrite or privilege escalation.
Negative signals:
* No host-admin penalty applied. There is no evidence that host-admin privilege is required for the complete vulnerable operation.
* No niche or hardware penalty applied. iwlwifi and WoWLAN are hardware-specific, but the supplied evidence does not establish rare physical-only hardware as a material exploitation restriction.
* No hard-race penalty applied. This is a validation and length-handling issue, not a demonstrated timing race.
Important non-awarded signals:
* Controlled reclaim or attacker-controlled kernel object replacement is not demonstrated.
* Arbitrary or directed kernel write is not demonstrated.
* A reliable kernel crash is not explicitly demonstrated by the patch, so no separate DoS point is awarded.
* Confidentiality and integrity impact are not awarded merely because an underflow might reach skb copying.
* Direct remote network reachability is not established. The appropriate possible exposure model is firmware-mediated adjacent wireless influence, not AV:N.
* Local unprivileged trigger is not established because the complete ability to induce the malformed firmware report is not shown.
* Strong LPE plausibility is not awarded. No credential, callback, refcount takeover, active-object replacement, or security-boundary primitive is demonstrated.
3. Reachability analysis
The affected path is `iwl_mvm_report_wakeup_reasons()` in the iwlwifi WoWLAN resume or wakeup-report handling path. The immediate input is not a normal host network packet directly processed from an attacker socket. It is packet metadata and packet data reported by Intel WiFi firmware after a WoWLAN wake event.
A plausible attacker model is a nearby WiFi actor sending crafted 802.11 frames while the target has WoWLAN enabled and the wireless device is suspended or entering a wakeup path. However, the supplied patch does not prove that an over-the-air frame can reliably cause firmware to report a `pktsize` shorter than the derived 802.11 header, IV, and ICV lengths. A malformed report may instead require a firmware defect, corrupted firmware state, or a specific device/firmware implementation behavior.
Host-admin privilege is therefore `UNKNOWN`. No host privilege is shown to be necessary for an adjacent attacker to transmit wireless frames, but the full trigger chain through firmware is not established. Namespace-scoped privilege is also `UNKNOWN`, since network namespaces do not control the physical WiFi firmware wakeup-report path. WoWLAN must be enabled and the affected Intel iwlwifi hardware and firmware path must be active.
4. Primitive and severity interpretation
The direct primitive is an integer-underflow and insufficient-length-validation condition in a kernel packet reconstruction path. Before the fix, `pktsize` could be smaller than the required 802.11 header, IV, and ICV lengths. The code copied header bytes into an skb and then subtracted header and encryption-related lengths without first validating that the total was representable.
This is not a UAF and does not involve stale object lifetime management. It is a possible out-of-bounds read or constrained skb buffer overwrite candidate. The patch moves the header copy after validation and rejects `pktsize <= hdrlen + ivlen + icvlen`, which strongly indicates that the prior ordering could use an invalid length. However, the provided context does not include the skb allocation size or all later `pktsize` consumers, so controlled kernel-memory corruption is not established.
The issue is classified as `CLASS_B` because a potentially exploitable kernel memory-handling primitive exists, but attacker control, overwrite target control, and practical reachability through firmware remain unresolved. It is not `CLASS_A` because there is no demonstrated controlled overwrite, arbitrary write, controlled reclaim, callback influence, information disclosure, or privilege escalation.
`ImportantCandidate=NO` is appropriate because the demonstrated mechanics do not yet establish meaningful exploitation leverage beyond a potentially crash-capable invalid memory operation. `AutoDowngradeAllowed=YES` is appropriate because this is currently a constrained firmware-mediated corruption candidate without proof of a reliable attacker-controlled trigger or post-corruption primitive. Manual review remains recommended to inspect the full function, skb allocation path, firmware wakeup notification format, and whether malformed over-the-air frames can cause inconsistent packet length reporting.
5. One-sentence report phrase
A firmware-reported WoWLAN packet length could be smaller than the derived 802.11 header and encryption overhead, causing integer underflow and potentially unsafe skb data handling, but practical attacker control through the WiFi firmware reporting path requires further validation.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
The patch fixes a kernel packet-length underflow before skb copying, but the supplied context does not establish whether a nearby attacker can reliably induce the malformed firmware report or whether the resulting invalid length reaches a controllable overwrite sink.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: wifi: iwlwifi: mvm: fix a possible underflow [ Upstream
Commit: 38ad8339211bf24c19126ec7629ea52094676454
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=38ad8339211bf24c19126ec7629ea52094676454
Changed files:
drivers/net/wireless/intel/iwlwifi/mvm/d3.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=38ad8339211bf24c19126ec7629ea52094676454
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-93792 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93792
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:N/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: 2
Paranoid ActionableScore: 3
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: NO
Published priority for this report (same as in Subject): MODERATE REGULAR
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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