[CVE-2026-68419][MODERATE 7.0] RDMA/irdma: Prevent rereg_mr for non-mem regions [ Upstream

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

CVE: CVE-2026-68419
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: RDMA/irdma: Prevent rereg_mr for non-mem regions [ Upstream
Commit: fb46d134e1b8690bed2da9005b36d32d2efd34ac
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fb46d134e1b8690bed2da9005b36d32d2efd34ac
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68419
Analysis date: Mon, 10 Aug 2026 10:18:54 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A local process with RDMA uverbs access can invoke rereg_mr on special irdma non-memory MR objects, causing a real CQP operation with mkey 0 and potentially corrupting RDMA device registration state or causing RDMA function DoS.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-68419 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68419

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-2026-68419	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	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-20;CWE-754;CWE-284;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '6.6';DESCR 'An irdma user memory region used for QP CQ or SRQ buffers can be passed to rereg_mr even though these special regions do not have a valid hardware mkey. This can make the driver submit a real CQP operation with the zero initialized mkey value 0, which may confuse device memory registration state or trigger adapter or driver failure. For the CVSS the PR:L is used because a local user or process with access to RDMA uverbs can create these objects and call rereg_mr. The issue is not network reachable through normal packet traffic and requires local RDMA device access on the target. Impact is at least local denial of service of the RDMA function. In the paranoid interpretation, limited confidentiality or integrity impact is kept because RDMA memory registration and mkey handling affect DMA access control, but there is no proven arbitrary write primitive in the patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)	YES	SIMPLEFIX NETWORK LINUS  DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7 DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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## 1. ActionableScore

ActionableScore=5
ActionableScoreLower=3

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

## 2. Signal breakdown

Conservative signals:

- Local unprivileged trigger: +1
  A local userspace process with access to RDMA uverbs can create the special MR objects and invoke rereg_mr. This is PR:L, not PR:H, if uverbs access is delegated by device permissions or container device passthrough.

- Memory corruption, weak or indirect corruption candidate: +1
  The bug causes a real CQP operation to be emitted for a special non-memory MR that has no valid hardware mkey, using the zero-initialized mkey value 0. This is not a proven UAF, OOB write, or arbitrary write, but it is an invalid hardware object state transition.

- Privileged kernel/device-management/DMA-adjacent path: +1
  The affected path is RDMA memory registration and hardware key management, where invalid mkey handling may affect DMA authorization or device resource state.

- Rare AND hardware-specific subsystem/configuration: -1
  This requires irdma hardware and RDMA userspace access. It is not a generic default kernel path.

- Availability impact realistic: +1
  A malformed CQP operation with mkey 0 can plausibly fail or destabilize RDMA device state, but no concrete host-wide kernel crash is shown.

Paranoid additional signals:

- Confidentiality impact plausible: +1
  RDMA mkey handling is part of memory access control. A bad mkey operation deserves review for unintended memory exposure, although no read primitive is demonstrated.

- Integrity impact plausible: +1
  RDMA registration state affects DMA permissions. Integrity impact is plausible enough for manual triage, but not proven as arbitrary write.

Validation-only cap applies: this is primarily a new EINVAL rejection of an unsupported object type. Conservative score is capped below Important, and paranoid score is capped at 5 because no concrete UAF, OOB write, type confusion, or arbitrary write primitive is shown.

## 3. Reachability analysis

The bug is locally reachable through RDMA uverbs when an application can create QP, CQ, or SRQ related special registrations and then call rereg_mr on the resulting MR object. It is not reachable through normal network packet traffic and should not be scored as remote.

Namespaces and containers may matter if RDMA device nodes are passed through or if a container has access to /dev/infiniband/uverbsX. In that case PR:L remains reasonable because the attacker is not full host root. In a locked-down deployment with no RDMA device access for untrusted users, practical exposure is much lower.

The path is not broadly default-exposed. It depends on Intel irdma hardware, the driver being loaded, and RDMA userspace access being available.

## 4. Severity interpretation

This behaves like an actionable Moderate issue rather than an ordinary Low because it affects RDMA memory registration and hardware mkey state, not just local bookkeeping. However, it is not a Strong Important candidate on the available patch evidence because the patch does not show attacker-controlled memory corruption, UAF reclaim, arbitrary write, or a demonstrated privilege escalation chain.

Theoretical risk exists around DMA access-control state because mkeys are security-relevant in RDMA. Realistic evidence supports local RDMA function/device DoS and a need for manual review, not confirmed LPE.

## 5. One-sentence report phrase

A local process with RDMA uverbs access can invoke rereg_mr on special irdma non-memory MR objects, causing a real CQP operation with mkey 0 and potentially corrupting RDMA device registration state or causing RDMA function DoS.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Manual review is required because the bug touches RDMA memory registration and hardware mkey handling, which are DMA access-control mechanisms, even though the patch currently supports only weak or indirect corruption rather than a proven privilege escalation primitive.

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

Patch: RDMA/irdma: Prevent rereg_mr for non-mem regions [ Upstream
Commit: fb46d134e1b8690bed2da9005b36d32d2efd34ac
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fb46d134e1b8690bed2da9005b36d32d2efd34ac

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=fb46d134e1b8690bed2da9005b36d32d2efd34ac

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

The original Linux kernel CVE announcement for CVE-2026-68419 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68419

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:N/I:N/A:L
  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).