[CVE-2025-38089][MODERATE 7.0] sunrpc: handle SVC_GARBAGE during svc auth processing as auth error

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

CVE: CVE-2025-38089
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: sunrpc: handle SVC_GARBAGE during svc auth processing as auth error
Commit: 599c489eea793821232a2f69a00fa57d82b0ac98
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=599c489eea793821232a2f69a00fa57d82b0ac98
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2025-38089
Analysis date: Wed, 16 Sep 2026 14:01:55 -0400
ActionableScore: 6
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2025-38089 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2025-38089

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-2025-38089	MODERATE	https://www.kernelcve.org/list/?q=CVE-2025-38089 CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H';CWE-824;**CWE-476;*CWE-787;Other CVSS 'AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H';BEST CVSS score: '9.8';DESCR 'A remotely triggerable memory corruption issue exists in the SUNRPC server authentication path because SVC_GARBAGE from svc_authenticate or pg_authenticate was handled as GARBAGE_ARGS. In this error path rq_accept_statp may not be initialized, but svc_process_common still dereferences it and stores rpc_garbage_args. On a fresh RPC server thread this can be NULL and cause a kernel crash. On reused threads the stale pointer may cause a memory scribble, so the impact is at least remote denial of service and may include confidentiality or integrity impact in a worst case memory corruption scenario. For the CVSS the PR:N is selected for the paranoid score because a crafted RPC packet can reach the vulnerable server path without local access or authenticated privileges when the kernel RPC service is exposed. The issue is network reachable for systems running kernel SUNRPC services such as NFS server endpoints, though many deployments restrict access to trusted storage or data center networks.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) 	MAYBE	REMOTE DANGER NETWORK KERNEL_PANIC_PLUS_UAF KPANIC PACKET  DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH	-	-	checked

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

ActionableScore=6
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 4
* Conservative score: 4
* Raw paranoid score: 6
* Paranoid score: 6
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

No floor or cap changed the conservative score. No floor or cap changed the paranoid score.

2. Signal breakdown

Conservative signals:

* +2 Remote reachable / directly network-triggerable: commit states a client can remotely trigger the crash by sending a specially crafted packet to a kernel RPC server.
* +1 Reliable kernel crash / strong DoS: if rq_accept_statp is NULL, svc_process_common dereferences it and stores through it, causing a kernel crash.
* +1 Weak / indirect corruption candidate: in non-first-use cases, rq_accept_statp can be stale or uninitialized and the code can store rpc_garbage_args through it, described as a memory scribble.
* Raw conservative score: 2 + 1 + 1 = 4.

Paranoid additional signals:

* +1 Weak LPE concern / unresolved stale write concern: this is not only a NULL dereference. The supplied evidence explicitly says stale rq_accept_statp may cause a memory scribble, which is a real kernel write-like corruption sink even though target and payload control are unclear.
* +1 Broadly deployed network service exposure in relevant environments: SUNRPC is used by kernel RPC services such as NFS server endpoints and can be exposed over the network in storage/server deployments.
* Raw paranoid score: 4 + 1 + 1 = 6.

Important non-awarded signals:

* RealUAF not awarded: the evidence establishes an uninitialized or stale pointer store, not an object use after free.
* CLASS_A not awarded: no arbitrary write, controlled reclaim, controlled target selection, callback hijack, credential overwrite, or demonstrated LPE is established.
* Controlled reclaim not demonstrated.
* Arbitrary read/write not demonstrated.
* Confidentiality impact not awarded as an ActionableScore signal because no disclosure path is shown.
* Integrity impact is represented only as unresolved memory scribble concern, not as proven attacker-controlled integrity compromise.
* Extra Availability not awarded because the same crash is already counted once.
* Race/timing penalty not applied because the trigger is a malformed RPC/auth processing path, not a demonstrated hard timing race.
* Host-admin penalty not applied because the attacker is a remote RPC client and no local host-admin prerequisite is shown.
* Repeated release/refcount signal not applicable: no first release, surviving exact reference, and second lifetime mutation is shown.

3. Reachability analysis

The evaluated attacker is a remote RPC client. The commit explicitly describes a remotely-triggerable crash from a specially crafted packet sent to a kernel RPC server. No local code execution, authenticated user context, or host administrator privilege is required to reach the vulnerable parsing/authentication path when the RPC service is exposed.

HostAdminRequired is NO because the complete trigger is remote packet delivery to the vulnerable kernel RPC server path. NamespaceScopedPrivilege is NO because the issue is not based on a namespace-scoped local capability chain.

A prior service setup is required in the operational sense: the system must be running a kernel SUNRPC based server endpoint such as an NFS server and the endpoint must be reachable by the attacker. This is an exposure condition, not attacker privilege. No special hardware, boot option, or local control-plane operation is indicated. No race repeatability issue is established.

4. Primitive and severity interpretation

The exact primitive is an uninitialized or stale pointer store through rq_accept_statp in svc_process_common after SVC_GARBAGE is returned during svc_authenticate or pg_authenticate. The old path treated this as GARBAGE_ARGS and executed:

* rqstp->rq_accept_statp = rpc_garbage_args

even though rq_accept_statp might not have been set for this error path.

This is not a RealUAF based on supplied evidence. It is an invalid stale/uninitialized pointer dereference with a fixed-value store. On a fresh RPC server thread, the pointer can be NULL and the demonstrated result is a kernel crash. On reused threads, the pointer may contain a prior value and the commit explicitly says it could create a memory scribble.

PrimitiveClass is CLASS_B because there is a real potentially exploitable kernel corruption primitive, but the useful exploitation leverage is unresolved. It is stronger than pure Class C crash-only behavior because the non-NULL case is described as memory scribble. It is not CLASS_A because there is no demonstrated attacker-directed target, attacker-controlled payload, controlled reclaim, arbitrary write, or privilege escalation.

ImportantCandidate is YES because the issue is remote, unauthenticated in the exposed-service model, and includes a kernel memory scribble possibility beyond the confirmed crash. AutoDowngradeAllowed is NO because automatically closing it as ordinary Moderate would discard an unresolved remote kernel corruption primitive. Likely operational severity is at least Actionable Moderate and may be Important after manual review depending on whether rq_accept_statp can be steered to sensitive storage or made to corrupt useful kernel state.

5. One-sentence report phrase

A remote client can send a crafted RPC packet that makes SUNRPC authentication return SVC_GARBAGE before rq_accept_statp is initialized, causing a NULL pointer dereference or possible stale pointer memory scribble in the kernel RPC server.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the bug is network reachable and includes a concrete memory scribble possibility, not just a NULL dereference DoS, but the degree of attacker control over the stale pointer target is unresolved.

7. Call-site confidence

Call-site confidence: high

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

Patch: sunrpc: handle SVC_GARBAGE during svc auth processing as auth error
Commit: 599c489eea793821232a2f69a00fa57d82b0ac98
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=599c489eea793821232a2f69a00fa57d82b0ac98

Commit description:

tianshuo han reported a remotely-triggerable crash if the client sends a
kernel RPC server a specially crafted packet. If decoding the RPC reply
fails in such a way that SVC_GARBAGE is returned without setting the
rq_accept_statp pointer, then that pointer can be dereferenced and a
value stored there.

If it's the first time the thread has processed an RPC, then that
pointer will be set to NULL and the kernel will crash. In other cases,
it could create a memory scribble.

The server sunrpc code treats a SVC_GARBAGE return from svc_authenticate
or pg_authenticate as if it should send a GARBAGE_ARGS reply. RFC 5531
says that if authentication fails that the RPC should be rejected
instead with a status of AUTH_ERR.

Handle a SVC_GARBAGE return as an AUTH_ERROR, with a reason of
AUTH_BADCRED instead of returning GARBAGE_ARGS in that case. This
sidesteps the whole problem of touching the rpc_accept_statp pointer in
this situation and avoids the crash.

Cc: stable@kernel.org
Fixes: 29cd292 ("SUNRPC: Fix encoding of accepted but unsuccessful RPC replies")
Reported-by: tianshuo han <hantianshuo233@gmail.com>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/sunrpc/svc.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=599c489eea793821232a2f69a00fa57d82b0ac98

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

The original Linux kernel CVE announcement for CVE-2025-38089 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2025-38089

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:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
  The Best / paranoid CVSS vector: AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 9.8

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: 4
  Paranoid ActionableScore: 6

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).