[CVE-2026-45964][LOW] SUNRPC: fix gss_auth kref leak in gss_alloc_msg error path

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

CVE: CVE-2026-45964
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: SUNRPC: fix gss_auth kref leak in gss_alloc_msg error path
Commit: 3b2b6c42070ce4204936288253baf101e995c2d3
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3b2b6c42070ce4204936288253baf101e995c2d3
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45964
Analysis date: Wed, 27 May 2026 19:07:29 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-45964 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45964

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-2026-45964	LOW	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-401;*CWE-772;CWE-404;CWE-703;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'SUNRPC auth_gss can leak a gss_auth reference when gss_alloc_msg() fails after kref_get() but before the message is fully initialized. The failing path frees the message and pipe version but did not drop the gss_auth kref, so repeated allocation failures can keep authentication objects alive indefinitely. For the CVSS the PR:L is used because a local user or workload may exercise NFS RPCSEC_GSS paths on an already configured system, although reliable triggering depends on allocation failure and memory pressure. The issue is not directly network reachable and does not provide a memory corruption primitive. Impact is availability only through resource leakage under repeated error conditions.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) 	MAYBE	REMOTE INIT SIMPLEFIX LEAK ERRORPATH NETWORK  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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

ActionableScore=1

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

2. Signal breakdown
* Availability/resource leak concern: +1. A leaked `gss_auth` kref can keep authentication objects alive indefinitely.
* Hard or unreliable condition: -1. Triggering depends on `kstrdup_const()` failing, i.e. allocation failure or memory pressure.
* Local workload requirement: +1. A local workload may exercise NFS/RPCSEC_GSS paths on an already configured system.
* Resource leak only. No memory corruption, UAF, OOB write, arbitrary write, information disclosure, or privilege escalation primitive is shown.
* Not directly network reachable. Remote NFS activity may indirectly exercise RPCSEC_GSS, but the leak depends on local allocation failure in the client/server kernel path.

3. Reachability analysis
The issue is reachable when SUNRPC GSS message allocation reaches the `service_name` path and `kstrdup_const()` fails. A local user or workload may create RPCSEC_GSS activity if the system is already configured for it, but reliable exploitation requires memory pressure. Namespaces do not materially improve reachability unless they can trigger the configured NFS/RPCSEC_GSS workload. There is no direct network packet primitive.

4. Severity interpretation
This behaves like a Low-like resource leak. The realistic impact is gradual memory/resource retention under repeated allocation-failure conditions. There is no theoretical or demonstrated path to memory corruption, confidentiality impact, integrity impact, or privilege escalation.

5. One-sentence report phrase
A SUNRPC auth_gss error path can leak a `gss_auth` reference when `kstrdup_const()` fails, causing only resource retention under memory-pressure conditions.

6. Manual review recommendation
NO MANUAL CHECK NEEDED. This is a resource leak on an allocation-failure path with no memory corruption, privilege escalation, information disclosure, or direct remote trigger.

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

Patch: SUNRPC: fix gss_auth kref leak in gss_alloc_msg error path
Commit: 3b2b6c42070ce4204936288253baf101e995c2d3
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3b2b6c42070ce4204936288253baf101e995c2d3

Commit description:

Commit 5940d1c ("SUNRPC: Rebalance a kref in auth_gss.c") added
a kref_get(&gss_auth->kref) call to balance the gss_put_auth() done
in gss_release_msg(), but forgot to add a corresponding kref_put()
on the error path when kstrdup_const() fails.

If service_name is non-NULL and kstrdup_const() fails, the function
jumps to err_put_pipe_version which calls put_pipe_version() and
kfree(gss_msg), but never releases the gss_auth reference. This leads
to a kref leak where the gss_auth structure is never freed.

Add a forward declaration for gss_free_callback() and call kref_put()
in the err_put_pipe_version error path to properly release the
reference taken earlier.

Fixes: 5940d1c ("SUNRPC: Rebalance a kref in auth_gss.c")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Hodges <git@danielhodges.dev>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/sunrpc/auth_gss/auth_gss.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=3b2b6c42070ce4204936288253baf101e995c2d3

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

The original Linux kernel CVE announcement for CVE-2026-45964 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45964

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:L/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 1

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).