[CVE-2026-89535][MODERATE 7.0] svcrdma: Reorder rpcrdma_rn_unregister before rdma_destroy_id [ Upstream

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

CVE: CVE-2026-89535
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: svcrdma: Reorder rpcrdma_rn_unregister before rdma_destroy_id [ Upstream
Commit: 9f2f5d0999364c7070306cd422d8babc2621070d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9f2f5d0999364c7070306cd422d8babc2621070d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89535
Analysis date: Sat, 12 Sep 2026 05:35:55 -0400
ActionableScore: 5
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-2026-89535 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89535

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.

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

CVE-2026-89535	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-89535 CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;**CWE-476;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'An svcrdma teardown race can leave the transport notification entry installed in the RDMA device xarray after rdma_destroy_id has already freed sc_cm_id. A concurrent ib_unregister_device notification walk can then dispatch svc_rdma_xprt_done against state that references the freed cm_id, making this a UAF candidate in the kernel RDMA server transport path. At minimum this can cause a local denial of service via kernel crash or teardown failure. In the worst still defensible interpretation, memory corruption from the stale notification path may allow confidentiality or integrity impact and should be reviewed manually. For the CVSS the PR:L is used for the paranoid score because delegated RDMA management, reduced capability root, container root, or service accounts may be able to influence the transport lifecycle without full host administration. The issue is not directly Internet reachable and practical triggering usually requires a local or trusted RDMA/NFS server environment with concurrent device unregister or reset activity.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)  SKIP CVE-2026-89535 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	REMOTE INIT UAF NETWORK HARDWARE KPANIC 	-	-	checked

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

ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 4
* Raw paranoid score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

Conservative floor applied: 3 -> 4 because a real UAF or lifetime violation is directly established and host-admin-equivalent reachability is not fully proven from the supplied evidence.

Paranoid floor applied: 4 -> 5 because the stale entry is not merely passive metadata. It remains installed in the RDMA device notification xarray and can cause callback dispatch against state referencing the freed cm_id.

2. Signal breakdown

Positive signals:

* +2 Real UAF / lifetime violation: rdma_destroy_id(sc_cm_id) can free the CM ID while the transport notification entry remains registered.
* +1 Reliable crash / strong DoS: concurrent ib_unregister_device can dispatch svc_rdma_xprt_done against state referencing the freed sc_cm_id, plausibly causing kernel fault or teardown failure.
* +1 Active notification / secondary index staleness: sc_rn remains installed in device rd_xa after the referenced sc_cm_id lifetime has ended, so later notification walkers may act on obsolete state.

Negative signals:

* -1 Hard teardown race for conservative score: the described failure requires a concurrent ib_unregister_device walk in the narrow window between rdma_destroy_id and rpcrdma_rn_unregister.

Important non-awarded signals:

* Controlled reclaim not demonstrated.
* Arbitrary read or write not demonstrated.
* Remote Internet reachability not established.
* Confidentiality and integrity bonuses not awarded from UAF alone.
* Concrete repeated release/refcount signal not awarded.
* Weak LPE not separately awarded.
* Extra Availability not awarded because the same crash is already counted once.

Repeated release/refcount check:

* First lifetime operation can end lifetime: yes, rdma_destroy_id can free sc_cm_id.
* Exact same reference survives: a transport state path still references sc_cm_id through the still registered notification entry.
* Second operation is a real lifetime/refcount mutation: no, the supplied evidence shows callback dispatch and stale use, not a second put/release/refcount mutation.
* +1 Concrete repeated release/refcount awarded: no.
* Paranoid repeated-refcount leverage +1 awarded: no.
* FLOOR 5 from repeated release/refcount applied: no.

3. Reachability analysis

The trigger involves svcrdma transport teardown and concurrent RDMA device unregister notification processing. Reliable attacker control is unresolved from the supplied patch alone.

A remote NFS/RDMA client may influence creation or teardown of server RDMA transports, but the critical concurrent ib_unregister_device event is usually associated with RDMA device removal, driver teardown, reset, or host-side device management. The supplied evidence does not prove that an ordinary remote client can cause the complete sequence.

HostAdminRequired is UNKNOWN rather than YES because the patch does not fully establish that only a host administrator can trigger all required stages. It is also not NO because below-host-admin complete reachability is not proven.

NamespaceScopedPrivilege is NO because no namespace-scoped capability path is established.

Prior setup likely includes an NFS/RDMA server environment and an RDMA device. This is not public Internet exposure by default. Race repeatability is uncertain and likely depends on teardown or device unregister timing.

4. Primitive and severity interpretation

The primitive is a real Class B kernel lifetime bug. The affected stale state is active structured RDMA transport state, not a fixed passive buffer. The vulnerable ordering leaves a notification entry registered after the CM ID it references has been destroyed.

This is stronger than an ordinary NULL dereference because another kernel walker can discover the stale registration and dispatch a callback into state associated with the freed object. However, the supplied evidence does not establish controlled reclaim, attacker-shaped replacement contents, callback hijack, arbitrary R/W, or demonstrated privilege escalation.

PrimitiveClass is CLASS_B. ImportantCandidate is YES because active notifier-visible stale object use leaves meaningful exploitation impact unresolved beyond a trivial immediate dereference. AutoDowngradeAllowed is NO because automatically closing this as ordinary crash-only DoS would discard a real lifetime/notification ordering primitive requiring manual review.

Likely operational severity is Actionable Moderate, with Strong Important candidacy depending on whether further call-site review shows exploitable post-free field consumption or below-host-admin triggerability.

5. One-sentence report phrase

An svcrdma teardown ordering bug can leave a transport notification entry registered after rdma_destroy_id frees sc_cm_id, allowing a concurrent RDMA device unregister walk to dispatch against stale state and causing at least a kernel crash or unresolved UAF-class lifetime corruption.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the patch directly fixes a UAF-class lifetime ordering bug involving an active RDMA notification entry and a freed CM ID, and the exploitation leverage is not sufficiently resolved to allow automatic downgrade.

7. Call-site confidence

Call-site confidence: medium

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

Patch: svcrdma: Reorder rpcrdma_rn_unregister before rdma_destroy_id [ Upstream
Commit: 9f2f5d0999364c7070306cd422d8babc2621070d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9f2f5d0999364c7070306cd422d8babc2621070d

Changed files:
  net/sunrpc/xprtrdma/svc_rdma_transport.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=9f2f5d0999364c7070306cd422d8babc2621070d

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

The original Linux kernel CVE announcement for CVE-2026-89535 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89535

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:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 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: 4
  Paranoid ActionableScore: 5

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).