[CVE-2026-72464][MODERATE REGULAR] xprtrdma: Repost Receive buffers for malformed replies [ Upstream

[CVE-2026-72464][MODERATE REGULAR] xprtrdma: Repost Receive buffers for malformed replies [ Upstream

[AL-KERNEL]

CVE: CVE-2026-72464
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: xprtrdma: Repost Receive buffers for malformed replies [ Upstream
Commit: ef6fb8a5c521f1a07f85202d13e8f2898f247362
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ef6fb8a5c521f1a07f85202d13e8f2898f247362
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72464
Analysis date: Sat, 15 Aug 2026 09:59:32 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum, not a Strong Important candidate
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-72464 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72464

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 REGULAR
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-2026-72464	MODERATE	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:N/I:N/A:H';**CWE-400;CWE-703;CWE-755;BEST CVSS score: '6.5';DESCR 'Malformed RPC/RDMA replies can drain the client posted Receive queue because the bad version and short reply exits recycle the reply buffer without reposting a replacement Receive. A remote RPC/RDMA peer can trigger this with a sustained stream of replies that are shorter than the fixed transport header or that use an unrecognized RPC/RDMA version. Once the posted Receive queue is exhausted, the transport can stall until reconnect and valid traffic can fail due to missing receive buffers. For the CVSS the PR:N is used because a remote RPC/RDMA peer can trigger the condition without a local account on the client. The issue is adjacent network reachable in typical deployments because RPC/RDMA is normally used on RDMA capable storage or data center fabrics rather than the public Internet. Impact is denial of service only, with no supported evidence of memory corruption, information disclosure, or privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum, not a Strong Important candidate (with actual score 4)	YES	REMOTE NETWORK  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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

ActionableScore=4
ActionableScoreLower=3

1. ActionableScore
* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Actionable Moderate at minimum, not a Strong Important candidate**::

2. Signal breakdown
* Remote reachable / network-triggerable: +2. A remote RPC/RDMA peer can send malformed replies that consume posted Receive buffers without replacing them.
* Reliable kernel/service DoS: +1. The Receive queue can be drained until the transport stalls or reconnect is needed.
* Availability impact realistic: +1 in the paranoid score. Sustained malformed replies can repeatedly disrupt the RPC/RDMA transport.
* Rare / configuration-dependent exposure: -1 in the conservative score. RPC/RDMA normally requires RDMA-capable storage or data-center networking and is not a default public Internet protocol.
* No memory corruption signal. The patch shows Receive buffer reposting logic and transport credit handling, not UAF, OOB write, double free, arbitrary write, or type confusion.
* No privilege escalation signal. The supported impact is transport DoS only.

3. Reachability analysis
A remote RPC/RDMA peer can trigger the issue by sending sustained malformed replies with a short fixed header or an unsupported RPC/RDMA version. No local account on the client is required, so the practical PR is none once the attacker can act as the peer or influence that RDMA connection. This is adjacent-network exposure rather than broad Internet exposure because RPC/RDMA is typically deployed on RDMA-enabled storage or internal data-center fabrics. Namespaces and containers are not the main factor here.

4. Severity interpretation
This behaves like an actionable Moderate remote DoS, not an Important memory-corruption issue. The bug is practically relevant because it is peer-triggerable and can stall the transport, but the patch does not support confidentiality impact, integrity impact, privilege escalation, or a kernel memory corruption primitive. The paranoid score keeps it in manual-review territory because network-triggerable RDMA storage transport failures can be operationally significant.

5. One-sentence report phrase
Malformed RPC/RDMA replies can drain the client posted Receive queue because bad-version and short-reply paths fail to repost Receive buffers, allowing a remote peer on an RPC/RDMA fabric to stall the transport until reconnect.

6. Manual review recommendation
MANUAL CHECK REQUIRED.
Reason: the issue is remotely triggerable by an RPC/RDMA peer and affects availability of a storage/RPC transport, even though the evidence supports DoS only and not privilege escalation.

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

Patch: xprtrdma: Repost Receive buffers for malformed replies [ Upstream
Commit: ef6fb8a5c521f1a07f85202d13e8f2898f247362
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ef6fb8a5c521f1a07f85202d13e8f2898f247362

Changed files:
  net/sunrpc/xprtrdma/rpc_rdma.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=ef6fb8a5c521f1a07f85202d13e8f2898f247362

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

The original Linux kernel CVE announcement for CVE-2026-72464 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72464

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:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 6.5

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: 4

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 REGULAR

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).