[CVE-2026-80709][MODERATE 7.0] s390/zcrypt: Fix wrong domain value verification with EP11 CPRBs

[CVE-2026-80709][MODERATE 7.0] s390/zcrypt: Fix wrong domain value verification with EP11 CPRBs

[AL-KERNEL]

CVE: CVE-2026-80709
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: s390/zcrypt: Fix wrong domain value verification with EP11 CPRBs
Commit: 4589f742718d0256ea6dd1f5a78be6e689bdb8aa
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4589f742718d0256ea6dd1f5a78be6e689bdb8aa
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80709
Analysis date: Fri, 28 Aug 2026 06:40:43 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
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-2026-80709 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80709

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-80709	MODERATE	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:L/I:L/A:H';CWE-125;CWE-129;*CWE-20;BEST CVSS score: '6.6';DESCR 'An out of bounds heap read can occur in s390/zcrypt when an EP11 administrative CPRB is processed on a custom device node with a domain value outside the real AP domain bitmap size. The code used AUTOSEL_DOM as the upper bound before testing a bit in perms adm, while the permissions bitmap is limited to AP_DOMAINS (256) entries. A local attacker with access to the relevant zcrypt device interface could supply an invalid domain and make the kernel read memory beyond the permissions bitmap. For the CVSS the PR:L value is used because reliable triggering requires a local process with access to the zcrypt custom device node, but not necessarily full root privileges in deployments where device access is delegated. The issue is not network reachable. Impact is at least local denial of service via a possible kernel fault, with limited confidentiality or integrity concern because an adjacent heap bit may influence the administrative permission decision.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)	YES	SIMPLEFIX HARDWARE LINUS  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=3

1. ActionableScore
* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

2. Signal breakdown
* Local limited-user trigger: +1. Triggering requires a local process able to access the relevant zcrypt custom device node and submit an EP11 administrative CPRB.
* Memory corruption, weak/indirect candidate: +1. The bug is an out-of-bounds heap read through `test_bit_inv(domain, perms->adm)`, not an OOB write or UAF.
* Integrity impact plausible: +1. The out-of-bounds bit read occurs in an administrative permission-check path, so adjacent heap data may influence whether an admin CPRB is rejected.
* Privileged device-management corruption path: +1. The affected code is in a trusted s390 crypto device path and checks custom-device administrative permissions.
* Rare and configuration-dependent exposure: -1. The issue requires s390 zcrypt, EP11/AP crypto hardware or compatible setup, and custom device nodes.
* Paranoid-only confidentiality or availability concern: +2. The OOB heap bit read may act as a limited heap-bit oracle or fault under some layouts, but no direct disclosure, write primitive, UAF reclaim, or arbitrary corruption is shown.

3. Reachability analysis
The bug is local, not network reachable. A realistic trigger needs access to a zcrypt custom device node and the ability to submit an administrative EP11 CPRB with an invalid domain value. Namespaces do not automatically make this reachable unless the device node is delegated into a container or service context. In typical systems without such s390 crypto hardware or without delegated zcrypt device access, exposure is low. If custom zcrypt devices are intentionally exposed to non-root service users, PR:L is appropriate.

4. Severity interpretation
This is not an ordinary crash-only bug because the OOB read is in an access-control decision for administrative CPRBs. It is also not a strong Important memory-corruption case because the patch shows a read-only bitmap over-index, with no OOB write, UAF, reclaim, callback control, or arbitrary write primitive. Conservative handling is Borderline / manual review recommended. Paranoid handling reaches Actionable Moderate because the bug combines heap OOB access with a permission-check path in a trusted crypto device subsystem.

5. One-sentence report phrase
An out-of-bounds heap read in s390 zcrypt EP11 administrative CPRB domain validation may let a local user with access to a custom zcrypt device influence an administrative permission check or trigger a fault, with no network reachability and no proven arbitrary memory corruption primitive.

6. Manual review recommendation
YES REQUIRES MANUAL CHECK. The issue should be reviewed manually because it is an OOB heap read in an administrative permission-check path, even though the demonstrated primitive appears limited and hardware/configuration dependent.

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

Patch: s390/zcrypt: Fix wrong domain value verification with EP11 CPRBs
Commit: 4589f742718d0256ea6dd1f5a78be6e689bdb8aa
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4589f742718d0256ea6dd1f5a78be6e689bdb8aa

Commit description:

There is a wrong upper limit check for the domain value when an EP11
CPRB is processed for sending to a crypto card. This check is only
active on custom device nodes but may lead to access heap memory
behind perms->adm when an administrative CPRB is sent.
Add correct limit (AP_DOMAINS = 256) checking to fix this.

Fixes: cfd68b3 ("s390/zcrypt: Filter admin CPRBs on custom devices")
Cc: stable@vger.kernel.org
Reviewed-by: Finn Callies <fcallies@linux.ibm.com>
Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/s390/crypto/zcrypt_api.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=4589f742718d0256ea6dd1f5a78be6e689bdb8aa

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

The original Linux kernel CVE announcement for CVE-2026-80709 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80709

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: Not available
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 6.6

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: 3
  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: NO
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).