[CVE-2026-64304][IMPORTANT] crypto: qat - validate RSA CRT component lengths [ Upstream

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

CVE: CVE-2026-64304
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: crypto: qat - validate RSA CRT component lengths [ Upstream
Commit: 6d99c5fadd2df488103f64d6475b63ba6852202b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6d99c5fadd2df488103f64d6475b63ba6852202b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64304
Analysis date: Sat, 25 Jul 2026 06:16:28 -0400
ActionableScore: 8
ActionableScore lower bound: 6
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A crafted RSA CRT key can cause an out of bounds write in the Intel QAT RSA CRT setkey path because oversized CRT components underflow the right aligned memcpy offset into half size DMA buffers, making this a local kernel memory corruption issue with DoS and possible privilege escalation concern.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-64304 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64304

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
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CVE-2026-64304	IMPORTANT	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:H/I:H/A:H';*CWE-787;CWE-190;*CWE-20;CWE-131;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'An out of bounds write in the Intel QAT RSA CRT setkey path occurs because qat_rsa_setkey_crt allocates half size DMA buffers for CRT components but previously accepted component lengths up to the full modulus size. A crafted RSA CRT key with p, q, dp, dq, or qinv larger than half_key_sz can make the destination offset underflow before memcpy and write attacker controlled key bytes outside the DMA buffer. For the CVSS the PR:L is used because a local user or local process that can access the kernel crypto API and select the QAT RSA implementation may be able to submit such a key without full administrative privileges. The issue is not directly network reachable, although a local service that imports untrusted RSA private keys and uses the kernel QAT crypto path could expose it indirectly. Impact is at least a local denial of service via kernel memory corruption and in worst case may allow confidentiality or integrity impact due to an attacker influenced out of bounds write.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8)	YES	OOB DANGER SIMPLEFIX DMAorINTERRUPT IMPROVEONLY KPANIC MEMORY  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=8
ActionableScoreLower=6

## 1. ActionableScore

* Conservative score: 6
* Paranoid score: 8
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local process may be able to reach kernel asymmetric crypto through AF_ALG or another crypto API consumer if QAT RSA is registered and usable.
* Memory corruption, strong corruption primitive: +2. The patch fixes an explicit out of bounds memcpy caused by `half_key_sz - len` underflow.
* Weak LPE concern: +1. The overwrite payload is influenced by RSA CRT component bytes, but the overwritten target is not shown to be reliably selectable.
* Local unprivileged high-control kernel data-plane API refinement: +1. The affected path processes user-shaped crypto key material, potentially through AF_ALG.
* Privileged kernel/device-management memory corruption path: +1. The corruption occurs in a QAT driver path using DMA coherent buffers.
* Reliable kernel crash / strong DoS: +1. Kernel memory corruption in this path can realistically crash the host.
* Rare AND difficult-to-reach subsystem/configuration: -1. The issue requires Intel QAT hardware, the QAT driver, and RSA CRT acceleration use.

Paranoid additions / interpretation:

* Privilege escalation plausible: upgraded to +2 instead of +1 because this is an attacker-influenced kernel OOB write, not only a NULL dereference or warning.
* Integrity impact plausible: +1. The primitive writes outside the intended kernel DMA allocation.
* Conservative double-counting is avoided. The paranoid score is kept at 8 rather than higher because no arbitrary target selection, reclaim primitive, or working LPE chain is shown.

Call-site confidence: high. The vulnerable allocation and memcpy pattern are directly visible in the patch context.

## 3. Reachability analysis

The most realistic trigger is local: a user or local service supplies a crafted RSA CRT private key where one of `p`, `q`, `dp`, `dq`, or `qinv` is larger than `key_sz / 2`. If that key reaches the QAT RSA CRT implementation, the old code can underflow the destination offset and write outside the allocated DMA buffer.

This is not directly network reachable. Remote exposure would require an application or service that accepts untrusted private keys and passes them into the kernel QAT crypto path.

Namespace and container impact depends on whether the container can access AF_ALG or another path to the registered QAT algorithm. If only privileged host services can use the QAT RSA path, practical reachability is lower. If unprivileged AF_ALG access is available and QAT RSA is registered, PR:L is appropriate.

The path is hardware and configuration dependent because Intel QAT support and RSA CRT mode must be present.

## 4. Severity interpretation

This is not an ordinary Moderate correctness bug. It is an explicit kernel out of bounds write in a hardware crypto driver, with attacker-influenced input and DMA buffer adjacency.

Realistic impact is at least local kernel crash / DoS. Practical privilege escalation is not demonstrated, but the primitive is strong enough to require manual review because it is a controlled-length, attacker-influenced memcpy past a kernel allocation.

Overall this is an Actionable Moderate at minimum and a Strong Important candidate under paranoid triage.

## 5. One-sentence report phrase

A crafted RSA CRT key can cause an out of bounds write in the Intel QAT RSA CRT setkey path because oversized CRT components underflow the right aligned memcpy offset into half size DMA buffers, making this a local kernel memory corruption issue with DoS and possible privilege escalation concern.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the patch fixes a concrete OOB write memory corruption primitive in kernel driver code, and the input bytes are attacker-influenced even though target control and exploitability are not proven.

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UPSTREAM PATCH SUMMARY
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Patch: crypto: qat - validate RSA CRT component lengths [ Upstream
Commit: 6d99c5fadd2df488103f64d6475b63ba6852202b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6d99c5fadd2df488103f64d6475b63ba6852202b

Changed files:
  drivers/crypto/qat/qat_common/qat_asym_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=6d99c5fadd2df488103f64d6475b63ba6852202b

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

The original Linux kernel CVE announcement for CVE-2026-64304 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64304

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:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.8

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: 6
  Paranoid ActionableScore: 8

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).