* [CVE-2026-93161][LOW] crypto: qat - clear AES key schedule from stack [ Upstream
@ 2026-09-18 3:58 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-18 3:58 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-93161
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: crypto: qat - clear AES key schedule from stack [ Upstream
Commit: b9cf42622b30178f554fa74411eec67e02d70411
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b9cf42622b30178f554fa74411eec67e02d70411
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93161
Analysis date: Thu, 17 Sep 2026 23:58:45 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-93161 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93161
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-2026-93161 LOW https://www.kernelcve.org/list/?q=CVE-2026-93161 CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N';CWE-226;*CWE-200;CWE-212;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '4.7';DESCR 'An AES-XTS key schedule can remain on the kernel stack in the Intel QAT crypto path because qat_alg_xts_reverse_key() expands a temporary crypto_aes_ctx and did not explicitly clear it after use. The residual data is sensitive key material, but the patch does not show a direct kernel memory disclosure primitive by itself. For the CVSS the PR:L is used because practical abuse would require a local user or local process able to reach the relevant crypto path or combine it with a separate local stack disclosure condition. The issue is not directly network reachable. Impact is confidentiality only. The base score treats the exposure as limited because no direct read path is shown, while the paranoid score uses C:H because leaked AES key schedule material could be high value in systems using QAT AES-XTS acceleration.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) YES SIMPLEFIX HARDWARE NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=2
ActionableScoreLower=1
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 2
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate**::
No floor or cap changed the score.
2. Signal breakdown
Conservative signals:
* +1 Sensitive data remanence. The patch establishes that a temporary AES-XTS key schedule stored in `crypto_aes_ctx` may remain in a kernel stack frame after `qat_alg_xts_reverse_key()` returns.
Paranoid additional signals:
* +1 High-value cryptographic material. The residual data is derived AES key schedule material, so an independent kernel-stack disclosure path could make the impact more serious. This is a review-sensitivity point, not a direct disclosure primitive.
Non-awarded material signals:
* 0 Real UAF not awarded. No post-lifetime object use is shown.
* 0 Memory corruption not awarded. No OOB write, UAF, type confusion, refcount corruption, or object overwrite is shown.
* 0 Direct confidentiality disclosure not awarded. The patch does not establish that stack bytes are copied to userspace, network, device-visible output, logs, or another attacker-readable channel.
* 0 Integrity impact not awarded. No unauthorized modification of kernel state, files, credentials, policy, or protected objects is shown.
* 0 Availability impact not awarded. No crash, panic, WARN-to-fatal path, or resource exhaustion is shown.
* 0 Strong LPE or weak LPE concern not awarded. Sensitive stack residue alone does not establish a privilege-escalation primitive.
* 0 Remote reachability not awarded. This is a local kernel crypto path issue, not a packet-processing or network-triggered path by itself.
* 0 Hardware rarity penalty not applied. QAT is hardware-specific, but no score reduction is applied solely because the code is in a driver.
3. Reachability analysis
The affected function is in the Intel QAT AES-XTS crypto implementation. A caller that causes AES-XTS key setup or reverse-key preparation through the QAT crypto path can create the residual key schedule on the kernel stack.
The supplied patch does not establish who can reliably reach this path in the evaluated deployment. It may be reached through kernel consumers of the crypto API, for example storage encryption or other configured users of AES-XTS acceleration, but those may require prior administrator setup. It may also be indirectly reachable by local processes if the relevant crypto interface is exposed, but that complete path is not established by the supplied context.
HostAdminRequired is therefore UNKNOWN. Below-host-admin reachability is not proven, but host-admin-equivalent privilege is also not positively established as a complete requirement.
NamespaceScopedPrivilege is UNKNOWN. No namespace-scoped capability path is shown.
There is no race. No special timing is required. Special QAT hardware and AES-XTS support are relevant deployment prerequisites, but the bug itself is a missing explicit wipe of stack-resident key schedule material.
4. Primitive and severity interpretation
The exact issue is sensitive-data remanence on the kernel stack. `qat_alg_xts_reverse_key()` expands the forward AES-XTS key into a temporary `crypto_aes_ctx`, copies the needed reverse-key material, and previously returned without clearing the temporary expanded schedule. The fix adds `memzero_explicit()` so the compiler cannot optimize away the clearing operation.
This is not an active structured UAF, fixed stale storage UAF, repeated release, RCU lifetime mismatch, authorization bypass, COW violation, or memory-corruption primitive.
PrimitiveClass is NONE because no independently useful kernel corruption, lifetime, ownership, authorization, or disclosure primitive is established by the patch. The demonstrated consequence is that sensitive key-derived material may remain in stack memory longer than necessary.
The speculative consequence is disclosure of AES key schedule material if another vulnerability or diagnostic path can later expose the same stack contents. That can be security-relevant because the data is cryptographic key material. However, the supplied evidence does not establish that such a read-back path exists in this bug.
ImportantCandidate is NO because there is no demonstrated disclosure path, corruption primitive, boundary bypass, or LPE chain. ManualReview is RECOMMENDED because cryptographic key material is involved and deployments using QAT AES-XTS acceleration may care about defense-in-depth hardening. AutoDowngradeAllowed is YES because the patch alone supports a low-like sensitive-data-remanence issue rather than an Important-class vulnerability.
Likely operational severity: low to ordinary moderate, depending on whether the product has any independent kernel stack disclosure surface and whether QAT AES-XTS is used for sensitive storage encryption workloads.
5. One-sentence report phrase
An AES-XTS key schedule could remain in a kernel stack frame in the Intel QAT crypto path because `qat_alg_xts_reverse_key()` did not explicitly clear the temporary expanded key context after use.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
Reason: the patch does not establish a direct leak or memory corruption primitive, but the residual data is cryptographic key material, so affected deployments using QAT AES-XTS should verify exposure and crypto-interface reachability.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: crypto: qat - clear AES key schedule from stack [ Upstream
Commit: b9cf42622b30178f554fa74411eec67e02d70411
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b9cf42622b30178f554fa74411eec67e02d70411
Changed files:
drivers/crypto/qat/qat_common/qat_algs.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=b9cf42622b30178f554fa74411eec67e02d70411
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-93161 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93161
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:H/PR:L/UI:N/S:U/C:L/I:N/A:N
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
The Best / paranoid CVSS score: 4.7
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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