[CVE-2026-80836][MODERATE 7.0] crypto: virtio - bound the akcipher result length

[CVE-2026-80836][MODERATE 7.0] crypto: virtio - bound the akcipher result length

[AL-KERNEL]

CVE: CVE-2026-80836
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: crypto: virtio - bound the akcipher result length
Commit: 5545de5050cbc3594506d74f2c392b0716cf8bca
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5545de5050cbc3594506d74f2c392b0716cf8bca
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80836
Analysis date: Fri, 04 Sep 2026 14:29:29 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-80836 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80836

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: YES

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

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

CVE-2026-80836	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80836 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:N/A:L';CWE-125;CWE-126;*CWE-200;*CWE-20;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N';BEST CVSS score: '7.1';DESCR 'A kernel heap out of bounds read in the virtio crypto akcipher callback occurs because the result length reported by the virtio crypto backend is assigned to akcipher_req dst_len without being bounded by the originally allocated destination buffer size. A malicious or non conforming backend can report a larger result length, causing sg_copy_from_buffer to read past vc_akcipher_req dst_buf and copy adjacent kernel heap bytes into the callers scatterlist. For the CVSS the PR:N is used in the paranoid virtualization threat model because a malicious virtio backend or device does not need privileges inside the guest OS, while the base local requester model can be treated as PR:L when a guest user must initiate the crypto request. The issue is not Internet network reachable and is specific to systems using virtio crypto with akcipher operations. Impact is primarily confidentiality loss through kernel heap information disclosure, with possible limited availability impact if the over read faults or destabilizes the guest kernel.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 6)  SKIP CVE-2026-80836 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	OOB VIRT SIMPLEFIX HARDWARE LINUS KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHERTHAN5 DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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

ActionableScore=6
ActionableScoreLower=5
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 5
* Conservative score: 5. No floor or cap applied.
* Raw paranoid score: 6
* Paranoid score: 6. No floor or cap applied.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

Conservative signals:

* +2: Strong disclosure primitive. The patch directly establishes an out-of-bounds kernel heap read because a device-reported akcipher result length is used as the copy length without being bounded to the originally allocated destination buffer.
* +1: Confidentiality plausible. The over-read bytes are copied by sg_copy_from_buffer() from the kernel heap buffer into the caller scatterlist, giving a concrete disclosure path.
* +1: Firmware/device-mediated external influence. The malicious or non-conforming virtio crypto backend controls the reported response length.
* +1: Practical exploit chain. The vulnerable length flows directly into the copy size and the copied data reaches the caller output buffer.

Paranoid additional signal:

* +1: In common configurations with a guest-accessible crypto requester path, such as a userspace crypto API or a guest service using akcipher, the requester may be able to observe the leaked output. This is not used as a conservative signal because the exact caller path is not shown in the patch.

Non-awarded signals:

* +0: RealUAF not awarded. No lifetime violation or stale object use is shown.
* +0: Arbitrary write not awarded. The patch shows an out-of-bounds read, not an overwrite.
* +0: Controlled reclaim not demonstrated.
* +0: Privilege escalation not demonstrated.
* +0: Reliable crash / strong DoS not awarded. A fault from the over-read is possible but not directly established as the primary behavior.
* +0: Remote network reachability not awarded. The issue is virtio-backend mediated, not Internet or packet reachable.
* +0: Extra availability not awarded. Any availability concern would be from the same over-read and is not independently demonstrated.
* +0: Memory layout invariant not separately counted because it is the same length-vs-buffer-size fact already counted as the OOB disclosure primitive.

3. Reachability analysis

The direct source of attacker-controlled input is the virtio crypto backend or device, which reports a result length larger than the original destination buffer. This is not a normal remote network attacker model. It is a virtualization or device-mediated model.

The complete practical scenario likely involves either a malicious or compromised backend, or a non-conforming device, plus a guest-side caller that submits an akcipher request and can observe the returned scatterlist data. The patch does not prove that an ordinary unprivileged local guest user can always reach the full path, so HostAdminRequired is UNKNOWN rather than NO. It also does not prove that host-admin-equivalent privilege is always required, because device-backed or delegated backend models may vary.

NamespaceScopedPrivilege is NO because no namespace-scoped capability path is involved. Prior setup requires a system using virtio crypto with akcipher support. No race is involved. No special physical-only hardware requirement is established, but the vulnerable path is feature-specific to virtio crypto.

4. Primitive and severity interpretation

The exact primitive is a kernel heap out-of-bounds read from vc_akcipher_req->dst_buf caused by trusting the backend-reported result length. The stale/lifetime rules do not apply because this is not a UAF.

This is a fixed buffer over-read with a concrete disclosure sink into the caller scatterlist. It is not a write primitive and does not by itself establish memory corruption, credential modification, callback control, or privilege escalation. The demonstrated consequence is kernel heap information disclosure. A limited availability effect is possible if the over-read faults, but this is secondary and not the main established primitive.

PrimitiveClass is CLASS_A because the patch establishes a concrete kernel heap disclosure path, not merely an internal invalid read. ImportantCandidate is YES because kernel heap disclosure from a device-controlled length can be security-relevant and should not be automatically downgraded. AutoDowngradeAllowed is NO because a concrete confidentiality primitive would be lost by automatic closure.

Likely operational severity is Actionable Moderate at minimum, with Strong Important review justified depending on whether the affected deployment exposes virtio crypto akcipher operations to an attacker-observable guest caller.

5. One-sentence report phrase

A virtio crypto backend can report an oversized akcipher result length, causing sg_copy_from_buffer() to over-read adjacent guest kernel heap memory into the caller scatterlist and potentially disclose sensitive kernel data.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the patch establishes a concrete kernel heap OOB read with a plausible disclosure path, and deployment-specific review is needed to determine who can control the backend response and who can observe the caller scatterlist output.

7. Call-site confidence

Call-site confidence: medium

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

Patch: crypto: virtio - bound the akcipher result length
Commit: 5545de5050cbc3594506d74f2c392b0716cf8bca
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5545de5050cbc3594506d74f2c392b0716cf8bca

Commit description:

virtio_crypto_dataq_akcipher_callback() sets the result length from the
device-reported response length without bounding it to the destination
buffer, which was allocated for the original request length.
sg_copy_from_buffer() then reads that many bytes from the destination
buffer; a backend reporting a larger length over-reads adjacent kernel
heap into the caller's scatterlist (an out-of-bounds read).

Clamp the reported length to the originally requested destination length.
A conforming device reports no more than that, so valid results are
unaffected.

Fixes: a36bd0a ("virtio-crypto: adjust dst_len at ops callback")
Cc: stable@vger.kernel.org
Signed-off-by: Bryam Vargas <hexlabsecurity@proton.me>
Message-ID: <20260622-b4-disp-3a2c09a8-v2-1-d1a809281db4@proton.me>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/crypto/virtio/virtio_crypto_akcipher_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=5545de5050cbc3594506d74f2c392b0716cf8bca

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

The original Linux kernel CVE announcement for CVE-2026-80836 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80836

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:H/I:N/A:N
  The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:L
  The Best / paranoid CVSS score: 7.1

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: 5
  Paranoid ActionableScore: 6

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).