[CVE-2026-74432][LOW] rxrpc: Fix leak of released call in recvmsg(MSG_PEEK)

[CVE-2026-74432][LOW] rxrpc: Fix leak of released call in recvmsg(MSG_PEEK)

[AL-KERNEL]

CVE: CVE-2026-74432
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: rxrpc: Fix leak of released call in recvmsg(MSG_PEEK)
Commit: 86eff3140c9d4b52bba13d1cba266da933403e51
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=86eff3140c9d4b52bba13d1cba266da933403e51
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74432
Analysis date: Sat, 15 Aug 2026 23:03:42 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-74432 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74432

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: LOW
Manual review required: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-74432	LOW	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:N/I:N/A:H';*CWE-401;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'rxrpc_recvmsg can leak a reference to an already released rxrpc call when recvmsg(MSG_PEEK) is used. The function holds a call reference regardless of MSG_PEEK, but the old error path skipped rxrpc_put_call for MSG_PEEK after RXRPC_CALL_RELEASED was observed. For the CVSS the PR:L is used because a local process must use an AF_RXRPC socket and call recvmsg(MSG_PEEK) to trigger the leak reliably. The issue is not directly network reachable as a standalone remote attack, although a remote rxrpc peer may influence call lifetime in normal protocol operation. Impact is denial of service through resource leakage under repeated triggering. No UAF, OOB access, information disclosure, or privilege escalation primitive is indicated by the patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)  SKIP CVE-2026-74432 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: 962fb1f651c2cf2083e0c3ef53ba69e3b96d3fbc YES  NO NO unknown 	MAYBE	SIMPLEFIX RACE LEAK LINUS  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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

ActionableScore=2

1. ActionableScore
* Conservative score: 2
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**

2. Signal breakdown
* Local unprivileged trigger: +1. A local process with access to AF_RXRPC can call recvmsg(MSG_PEEK) on the socket path.
* Real lifetime corruption: +1. This is a refcount lifetime bug where rxrpc_recvmsg() fails to drop a call reference in the MSG_PEEK path after RXRPC_CALL_RELEASED.
* Availability impact realistic: +1. Repeated triggering can leak rxrpc call objects and may eventually cause resource exhaustion.
* Rare AND difficult-to-reach subsystem/configuration: -1. RxRPC/AFS is not a broad default attack surface on many systems.
* No remote reachable signal. The peer may influence call lifetime, but the leak is reliably triggered by local recvmsg(MSG_PEEK).
* No memory corruption, UAF reclaim, OOB write, info leak, or privilege escalation signal is supported.

3. Reachability analysis
A local user process can plausibly trigger the bug if AF_RXRPC is enabled and usable. No administrative capability is indicated for the recvmsg(MSG_PEEK) operation itself, so PR is effectively local user level for triage. Namespace behavior does not materially increase severity unless AF_RXRPC is broadly exposed inside untrusted containers. The affected subsystem is relatively niche and not comparable to core TCP/IP, netfilter packet paths, io_uring, or page-cache paths.

4. Severity interpretation
This behaves like an ordinary Moderate or Low-like resource leak rather than an actionable memory-corruption CVE. The theoretical worst case is denial of service through accumulated leaked references, but the patch shows the opposite of UAF: an object is retained too long, not freed too early. There is no demonstrated primitive for confidentiality impact, integrity impact, privilege escalation, object replacement, callback control, or arbitrary write.

5. One-sentence report phrase
rxrpc_recvmsg() could leak a reference to an already released RxRPC call when MSG_PEEK is used, allowing a local user to cause resource exhaustion through repeated triggering, but no memory corruption or privilege escalation primitive is indicated.

6. Manual review recommendation
NO MANUAL CHECK NEEDED.
This is a localized refcount leak with DoS-only impact, niche subsystem exposure, and no supported memory corruption or security-boundary bypass primitive.

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

Patch: rxrpc: Fix leak of released call in recvmsg(MSG_PEEK)
Commit: 86eff3140c9d4b52bba13d1cba266da933403e51
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=86eff3140c9d4b52bba13d1cba266da933403e51

Commit description:

Fix rxrpc_recvmsg() to also drop the ref it holds on an already-released
call if MSG_PEEK is in force (the function holds a ref on the call
irrespective of whether MSG_PEEK is specified or not).

Fixes: 962fb1f ("rxrpc: Fix recv-recv race of completed call")
Link: https://sashiko.dev/#/patchset/20260616155749.2125907-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Jeffrey Altman <jaltman@auristor.com>
cc: Simon Horman <horms@kernel.org>
cc: linux-afs@lists.infradead.org
cc: stable@kernel.org
Link: https://patch.msgid.link/20260624163819.3017002-11-dhowells@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/rxrpc/recvmsg.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=86eff3140c9d4b52bba13d1cba266da933403e51

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

The original Linux kernel CVE announcement for CVE-2026-74432 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74432

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:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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: unknown
  Paranoid ActionableScore: 2

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).