[CVE-2026-74404][MODERATE 7.0] crypto: ccp - Fix snp_filter_reserved_mem_regions() off-by-one [ Upstream

[CVE-2026-74404][MODERATE 7.0] crypto: ccp - Fix snp_filter_reserved_mem_regions() off-by-one [ Upstream

[AL-KERNEL]

CVE: CVE-2026-74404
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: crypto: ccp - Fix snp_filter_reserved_mem_regions() off-by-one [ Upstream
Commit: 830c1f3e71989448652973375ef5e39b6ede47a3
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=830c1f3e71989448652973375ef5e39b6ede47a3
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74404
Analysis date: Sat, 15 Aug 2026 23:40:22 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
An off-by-one bounds check in AMD SEV-SNP reserved memory filtering can write one `sev_data_range` field past a page-sized kzalloc buffer, creating constrained kernel heap memory corruption in a privileged firmware/device initialization path.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-74404 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74404

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-2026-74404	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H';CWE-193;*CWE-787;CWE-122;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '6.4';DESCR 'An off by one bounds check in snp_filter_reserved_mem_regions can allow a page sized kzalloc buffer to be overrun when the reserved memory range list reaches the boundary case. The function checks the size of entries already present but does not account for the next sev_data_range entry before writing it, so the page_count field can be written past PAGE_SIZE. This is a kernel heap out of bounds write during AMD SEV SNP initialization rather than a pure warning or resource leak. For the CVSS the PR:H is used because reliable triggering normally requires administrative or platform level control over the reserved memory layout or driver initialization path. The issue is not directly network reachable. Impact is at least denial of service via kernel memory corruption and in the paranoid case may include confidentiality or integrity impact if the overflow corrupts a sensitive adjacent heap object.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)	YES	OOB SIMPLEFIX IMPROVEONLY LINUS MEMORY  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	YES	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

Conservative signals:

* +1 Firmware-mediated external influence: the affected list is built from reserved memory regions via `walk_iomem_res_desc()`, so practical attacker influence is more likely through platform firmware, memory map, or SEV-SNP platform state than through a normal local user API.
* +1 Constrained kernel buffer overwrite: the bug is an off-by-one bounds check that can write the `page_count` field past a `PAGE_SIZE` kzalloc buffer.
* +1 Privileged kernel/device-management memory corruption path: the corruption occurs in AMD CCP / SEV-SNP initialization code, a highly trusted firmware/device-management path.
* +1 Availability impact plausible: a heap OOB write in this path can plausibly crash or destabilize the host kernel.
* -1 Constrained payload / target: the overflow appears limited to a small kernel-derived structure field, with no demonstrated attacker-selected target, reclaim primitive, callback control, or arbitrary write.
* -1 Rare hardware/configuration exposure: this requires AMD SEV-SNP related initialization and a boundary case with many reserved memory regions.

Paranoid additions / interpretation:

* Treat the explicit heap OOB write as a strong enough kernel memory corruption primitive for manual triage sensitivity.
* +1 Confidentiality impact plausible and +1 Integrity impact plausible in the paranoid view, because corrupting an adjacent heap object in a privileged SEV-SNP path could theoretically affect sensitive kernel state.
* No remote/network trigger is supported.
* No direct local unprivileged trigger is supported.
* No strong LPE path is demonstrated.

Call-site confidence: medium. The changed function and allocation boundary are visible, but broader allocation adjacency and practical triggerability depend on platform memory layout and SEV-SNP initialization context.

## 3. Reachability analysis

The bug is not directly reachable from the network and does not appear reachable by an ordinary unprivileged local user. Triggering the boundary case likely depends on the host platform memory map, firmware-provided reserved regions, or privileged control over SEV-SNP initialization conditions.

Namespaces and containers do not materially lower the privilege requirement because this is not a namespace-scoped local API. A container user should not normally be able to influence the AMD-SP reserved memory region list or SEV-SNP firmware initialization path.

The path is not broad/default for all Linux systems. It is relevant to systems using AMD CCP / SEV-SNP support and only when the reserved range list reaches the vulnerable boundary condition.

## 4. Severity interpretation

This is not an ordinary resource leak or validation-only cleanup. The patch fixes an explicit kernel heap out-of-bounds write caused by failing to account for the entry about to be appended to a page-sized firmware argument buffer.

Realistic exploitation evidence is limited because the overwrite is small, the payload is constrained, and triggerability likely depends on firmware/platform state. However, because the primitive is real kernel memory corruption in a privileged SEV-SNP path, it should not be auto-closed as a low-risk correctness fix.

This behaves as an actionable Moderate at minimum, with paranoid handling justified for manual review. It is not a strong Important candidate unless additional evidence shows attacker-controlled reserved-region shaping, adjacent-object targeting, or a practical crash/LPE path.

## 5. One-sentence report phrase

An off-by-one bounds check in AMD SEV-SNP reserved memory filtering can write one `sev_data_range` field past a page-sized kzalloc buffer, creating constrained kernel heap memory corruption in a privileged firmware/device initialization path.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED.

Reason: the patch fixes an explicit kernel heap out-of-bounds write, even though the overwrite and trigger conditions appear constrained. This should receive manual review to confirm platform reachability, reserved-memory controllability, and whether adjacent heap corruption can produce more than DoS.

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

Patch: crypto: ccp - Fix snp_filter_reserved_mem_regions() off-by-one [ Upstream
Commit: 830c1f3e71989448652973375ef5e39b6ede47a3
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=830c1f3e71989448652973375ef5e39b6ede47a3

Changed files:
  drivers/crypto/ccp/sev-dev.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=830c1f3e71989448652973375ef5e39b6ede47a3

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

The original Linux kernel CVE announcement for CVE-2026-74404 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74404

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:H/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 6.4

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).