[CVE-2026-74390][MODERATE 7.0] RDMA/irdma: Fix out-of-bounds write in irdma_copy_user_pgaddrs [ Upstream

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

CVE: CVE-2026-74390
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: RDMA/irdma: Fix out-of-bounds write in irdma_copy_user_pgaddrs [ Upstream
Commit: 4780f58672ee6328accd54a95f9c00683477e499
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4780f58672ee6328accd54a95f9c00683477e499
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74390
Analysis date: Sat, 15 Aug 2026 15:11:16 -0400
ActionableScore: 8
ActionableScore lower bound: 6
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A local user with access to the irdma RDMA verbs device can trigger an out-of-bounds write past the fixed pgaddrmem array during PBLE setup by providing a umem with more DMA blocks than the lvl 0 path can store, causing kernel memory corruption with at least DoS impact and plausible privilege escalation risk.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-74390 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74390

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-2026-74390	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:H/I:H/A:H';*CWE-787;*CWE-20;CWE-119;BEST CVSS score: '7.8';DESCR 'An out-of-bounds write in the RDMA/irdma user verbs path can occur because irdma_copy_user_pgaddrs copied all DMA blocks from a user umem while the lvl 0 path stores entries in the fixed size iwmr pgaddrmem array. A local process with access to the irdma RDMA device can provide a umem with more DMA blocks than the fixed lvl 0 storage can hold, which can corrupt adjacent kernel memory. For the CVSS the PR:L because triggering requires local access to RDMA user verbs or the RDMA device file, but full root privileges are not necessarily required when uverbs access is delegated to users or containers. The issue is not directly network reachable because the vulnerable operation is a local control path for memory registration or ring setup rather than remote packet processing. Impact is at least local denial of service via kernel memory corruption and in worst case may allow privilege escalation, so confidentiality, integrity, and availability are rated high.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8)	YES	WRITE OOB SIMPLEFIX NETWORK DMAorINTERRUPT HARDWARE KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP	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 score:

* Local unprivileged trigger: +1. A local process with access to the irdma RDMA userspace verbs device can influence the umem and ring setup path.
* Constrained kernel buffer overwrite: +1. The bug is an explicit out-of-bounds write past the fixed 4 entry `iwmr->pgaddrmem` array, but the written values are DMA addresses rather than a fully arbitrary payload.
* Weak LPE concern: +1. Kernel memory corruption is present, but the patch does not demonstrate target selection, reclaim, callback overwrite, or an arbitrary write primitive.
* Reliable kernel crash / strong DoS: +1. Writing past a fixed kernel array can realistically corrupt adjacent state and crash the kernel.
* RDMA API with DMA mapping influence: +1. The user controlled umem layout affects how many DMA block addresses are copied.
* Privileged kernel/device-management memory corruption path: +1. The corruption is in an RDMA driver PBLE/PBL setup path and affects DMA-adjacent kernel metadata.
* Rare / hardware-specific exposure: -1. The issue requires affected Intel irdma hardware and access to the RDMA device.

Paranoid delta:

* Memory corruption, strong corruption primitive: upgrade to +2. The patch explicitly fixes an out-of-bounds write in kernel memory.
* Strong LPE plausibility: upgrade to +2. Local kernel OOB writes in driver object state can plausibly become privilege escalation even when the exact primitive is not demonstrated.
* Confidentiality impact plausible: +1. If the corruption is exploitable as LPE, confidentiality impact follows.
* Integrity impact plausible: +1. Kernel memory corruption can plausibly affect integrity in the paranoid interpretation.

## 3. Reachability analysis

The bug is locally reachable through RDMA userspace verbs or related object creation paths when the system has an affected irdma device and exposes `/dev/infiniband/uverbs*` to the attacker. Full root privileges are not necessarily required in deployments where RDMA access is delegated to users, service accounts, containers, or HPC workloads. It is not directly network reachable because the vulnerable path is local memory registration or queue object setup, not remote packet processing. Namespace and container setups matter because device passthrough or delegated uverbs access can reduce the practical privilege requirement to PR:L.

Call-site confidence: high. The patch includes both the vulnerable helper and the caller, showing that `lvl == 0` selects the fixed `pgaddrmem` buffer and that the old loop could exceed its length.

## 4. Severity interpretation

This is not an ordinary Moderate cleanup. It is an explicit kernel out-of-bounds write in a device driver path reachable from local RDMA userspace interfaces. Realistic exploitation evidence is limited because the overwrite payload and adjacent target are not shown to be fully attacker-controlled, so the conservative score stays in Actionable Moderate range. The paranoid score is Strong Important candidate because local kernel OOB writes have a plausible LPE risk and should not be auto-closed.

## 5. One-sentence report phrase

A local user with access to the irdma RDMA verbs device can trigger an out-of-bounds write past the fixed pgaddrmem array during PBLE setup by providing a umem with more DMA blocks than the lvl 0 path can store, causing kernel memory corruption with at least DoS impact and plausible privilege escalation risk.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED. This is an explicit kernel OOB write in an RDMA driver with local user-controlled input and plausible LPE impact, even though the exact overwrite target and payload control need manual validation.

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UPSTREAM PATCH SUMMARY
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Patch: RDMA/irdma: Fix out-of-bounds write in irdma_copy_user_pgaddrs [ Upstream
Commit: 4780f58672ee6328accd54a95f9c00683477e499
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4780f58672ee6328accd54a95f9c00683477e499

Changed files:
  drivers/infiniband/hw/irdma/verbs.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=4780f58672ee6328accd54a95f9c00683477e499

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DETAILED REPORT METHODOLOGY
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The original Linux kernel CVE announcement for CVE-2026-74390 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74390

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: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: 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).