* [CVE-2026-89539][LOW] SUNRPC: reject duplicate CREDS_VALUE options
@ 2026-09-12 6:24 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-12 6:24 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-89539
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: SUNRPC: reject duplicate CREDS_VALUE options
Commit: f615b884310bf82d0014e3b5a92eb9aa88146685
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f615b884310bf82d0014e3b5a92eb9aa88146685
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89539
Analysis date: Sat, 12 Sep 2026 02:24:39 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89539 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89539
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-2026-89539 LOW https://www.kernelcve.org/list/?q=CVE-2026-89539 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:N/I:N/A:H';*CWE-401;*CWE-772;*CWE-20;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'A duplicate CREDS_VALUE option in a SUNRPC RPCGSS upcall reply can make gssx_dec_option_array() call gssx_dec_linux_creds() more than once for the same svc_cred. Each call can install a new group_info allocation into creds cr_group_info, so the second decoded option overwrites the first pointer and leaks the first allocation. For the CVSS the PR:L is used for the paranoid score because a compromised or misconfigured local GSS upcall responder or delegated service context may be sufficient in some deployments, while typical direct triggering requires privileged local control of the upcall reply path. The issue is not directly network reachable from ordinary NFS or SUNRPC traffic unless an attacker can influence the local RPCGSS upcall response. Impact is resource exhaustion DoS after repeated malformed replies. No UAF, OOB access, arbitrary write, information disclosure, or privilege escalation primitive is evident from the code change.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) YES REMOTE LEAK NETWORK LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=2
ActionableScoreLower=1
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 2
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate**::
No floor or cap changed the score.
2. Signal breakdown
Conservative positive signals:
* +1 Concrete persistent kernel resource/reference leak. A duplicate CREDS_VALUE option can cause gssx_dec_linux_creds() to install a second group_info into the same svc_cred and orphan the first allocation, leaving its reference unreleased.
Conservative negative signals:
* No negative privilege penalty applied. Host-admin-equivalent triggering is not positively established from the supplied evidence.
* No race or hard timing penalty applied. The bug is an ordered duplicate-option decode, not a timing race.
* No niche-subsystem penalty applied. The limiting factor is the upcall reply path, not subsystem rarity by itself.
Paranoid additional signal:
* +1 Resource exhaustion plausibility. Repeated malformed upcall replies could accumulate leaked kvmalloc-backed group_info storage and cause availability impact through memory pressure.
Important non-awarded signals:
* RealUAF not awarded. The first group_info is leaked, not used after free.
* Concrete repeated release/refcount not awarded. The bug overwrites a pointer and loses a reference, but does not perform a second put or release through a dangling reference.
* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* Information disclosure not demonstrated.
* Integrity impact not demonstrated.
* Remote reachability not established from ordinary NFS or SUNRPC network traffic.
* Reliable kernel crash not awarded. The demonstrated primitive is leakage and potential resource exhaustion, not immediate panic.
* ImportantCandidate not awarded because this is a resource leak without memory corruption, ownership violation, authorization bypass, or unresolved post-lifetime mutation.
3. Reachability analysis
The affected parser processes a wire-format option array in a SUNRPC RPCGSS upcall reply. The supplied text indicates the malformed duplicate CREDS_VALUE entries are in the reply consumed by gssp_accept_sec_context_upcall(), not directly in normal NFS client or server packet processing.
The complete attacker boundary is therefore unresolved. A direct network attacker sending ordinary NFS or SUNRPC traffic is not shown to control this reply. Practical triggering appears to require influence over the local RPCGSS upcall responder, a compromised helper, a misconfigured service context, or equivalent local control of the authentication upcall reply path.
HostAdminRequired is UNKNOWN because the evidence does not prove that only host root or a host-admin-equivalent actor can supply the malformed reply, but it also does not establish ordinary unprivileged reachability. NamespaceScopedPrivilege is NO because no namespace-scoped capability path is established or relevant in the supplied material. No special hardware, boot option, or timing race is involved.
4. Primitive and severity interpretation
The exact primitive is a persistent reference and memory leak. gssx_dec_option_array() can accept more than one CREDS_VALUE option and call gssx_dec_linux_creds() repeatedly on the same svc_cred. The second decode overwrites creds->cr_group_info, while the first group_info allocation is no longer reachable by the normal free_svc_cred() cleanup path.
This is not active structured stale-object use. It is not fixed stale storage either. It is a lost-reference resource leak. There is no concrete UAF, no second lifetime mutation through a dangling reference, no OOB access, no controlled overwrite, and no authorization bypass.
Demonstrated consequence is memory leakage. Speculative consequence is denial of service through repeated accumulation of leaked group_info allocations. Leverage beyond resource exhaustion is not supported by the patch or supplied context.
PrimitiveClass is NONE because no meaningful corruption, stale-use, ownership, or authorization primitive is established. ImportantCandidate is NO because the issue does not preserve an Important-grade primitive and does not require unresolved memory-corruption review. AutoDowngradeAllowed is YES because the issue is a resource leak without evidence of memory corruption, privilege escalation, or security-boundary bypass.
Likely operational severity is ordinary Low to Moderate, depending on whether an attacker can repeatedly influence the local RPCGSS upcall reply path.
5. One-sentence report phrase
A duplicate CREDS_VALUE option in a SUNRPC RPCGSS upcall reply can overwrite svc_cred.cr_group_info and leak the first group_info allocation, causing potential resource exhaustion DoS if malformed replies can be supplied repeatedly.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
Reason: the patch establishes a concrete resource leak only, with no UAF, repeated stale refcount mutation, arbitrary write, disclosure, authorization bypass, or demonstrated privilege escalation.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: SUNRPC: reject duplicate CREDS_VALUE options
Commit: f615b884310bf82d0014e3b5a92eb9aa88146685
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f615b884310bf82d0014e3b5a92eb9aa88146685
Commit description:
gssx_dec_option_array() walks the wire-supplied option array and, for
every entry whose name matches CREDS_VALUE, calls
gssx_dec_linux_creds() on the same struct svc_cred. That helper
unconditionally installs a fresh groups_alloc() result into
creds->cr_group_info without releasing whatever pointer was already
there:
for (i = 0; i < count; i++) {
... decode name ...
if (length == sizeof(CREDS_VALUE) &&
memcmp(p, CREDS_VALUE, sizeof(CREDS_VALUE)) == 0) {
err = gssx_dec_linux_creds(xdr, creds);
...
}
}
A reply that carries two CREDS_VALUE entries therefore overwrites
cr_group_info on the second iteration and orphans the group_info
allocated by the first call. The earlier free_creds path only
releases the last cr_group_info via free_svc_cred(), so the first
allocation's refcount stays at one and its kvmalloc-backed storage
is leaked. No in-tree caller of gssp_accept_sec_context_upcall()
expects more than one CREDS_VALUE per reply.
Fix by tracking whether a CREDS_VALUE option has already been
decoded and returning -EINVAL on any subsequent match, so the
free_creds path releases the single group_info that was installed.
Fixes: 1d65833 ("SUNRPC: Add RPC based upcall mechanism for RPCGSS auth")
Cc: [email protected]
Assisted-by: kres (claude-opus-4-7)
Signed-off-by: Chris Mason <[email protected]>
Reviewed-by: Jeff Layton <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Chuck Lever <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
net/sunrpc/auth_gss/gss_rpc_xdr.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=f615b884310bf82d0014e3b5a92eb9aa88146685
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89539 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89539
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:H/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: 1
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
^ permalink raw reply [relevance 21%]
Results 1-1 of 1 | reverse | sort options + mbox downloads above
-- links below jump to the message on this page --
2026-09-12 6:24 21% [CVE-2026-89539][LOW] SUNRPC: reject duplicate CREDS_VALUE options AL-KERNEL
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox