[CVE-2026-93267][MODERATE REGULAR] RDMA/core: Fix potential use after free in uverbs_free_dmah() [ Upstream

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

CVE: CVE-2026-93267
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: RDMA/core: Fix potential use after free in uverbs_free_dmah() [ Upstream
Commit: 8b22722f45a29a7c0900b1d4d0bc5da5492ece10
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8b22722f45a29a7c0900b1d4d0bc5da5492ece10
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93267
Analysis date: Thu, 24 Sep 2026 20:34:23 -0400
ActionableScore: 4
ActionableScore lower bound: unknown
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-93267 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93267

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 REGULAR
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-2026-93267	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-93267 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:L/I:L/A:H';*CWE-416;CWE-362;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A race in RDMA DMAH destruction can leave a DMAH object reachable through the restrack netlink path after vendor specific resources have been released. A local attacker who can create and destroy DMAH objects and issue concurrent RDMA resource tracking requests may trigger a use-after-free, causing at least a kernel crash. For the CVSS the PR:L is selected because reliable triggering requires local access to an RDMA uverbs device and a user context capable of creating DMAH objects. The race requires timing control and therefore AC:H. The issue is not directly network reachable. Impact is at least local denial of service. Limited confidentiality or integrity impact is plausible in the worst case because this is an explicit use-after-free involving vendor specific resources. The actual impact depends on the affected RDMA driver and requires manual review.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4)	YES	INIT UAF NETWORK LINUS MEMORY  DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP	YES	NO	checked

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

ActionableScore=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 2
* Conservative score: 4
* Raw paranoid score: 2
* Paranoid score: 4
* Applied conservative floor: 2 -> 4. A concrete UAF is directly implied, host-admin-equivalent privilege is not positively established, and the stale object remains reachable through a live netlink resource-tracking path.
* Applied paranoid floor: 2 -> 4.
* Final recommended bucket: **Borderline / manual review recommended**::

2. Signal breakdown

* +2 Real UAF or active lifetime violation. The patch explicitly states that a DMAH remains reachable through restrack after vendor-specific resources associated with that DMAH have been released. A netlink caller can obtain the object through rdma_restrack_get during this interval.
* No local unprivileged trigger point awarded. The supplied material does not establish that an ordinary unprivileged user can both create and destroy DMAH objects and access the relevant RDMA netlink resource-tracking operation.
* No remote reachability point awarded. RDMA netlink access is a local kernel control-plane path, not direct network packet processing.
* No attacker-controlled reclaim, replacement, arbitrary write, callback control, disclosure, or refcount takeover is demonstrated.
* No structured stale-object leverage point awarded. The stale use may access released vendor-specific resources, but the supplied patch does not show which fields are later consumed or whether an attacker can shape post-free replacement state.
* No repeated release or refcount mutation point awarded. The patch shows one teardown flow and does not establish a second put, free, or refcount operation through the exact same dangling reference.
* No confidentiality or integrity point awarded. The possibility of a UAF alone does not establish a disclosure or modification primitive.
* No hard-race penalty applied. The commit describes a short window, but the supplied material does not establish that it is one-shot, externally uncontrollable, or materially difficult to repeat.
* No niche-subsystem penalty applied. RDMA is specialized, but the evidence does not establish a rare-hardware or inaccessible deployment prerequisite.

3. Reachability analysis

The evaluated attacker is a local process interacting with an RDMA uverbs device and the RDMA netlink resource-tracking interface. The complete privilege boundary is unresolved from the supplied patch.

DMAH creation and destruction require access to an RDMA device through uverbs. Access permissions for uverbs devices are deployment-specific. The netlink resource-tracking query path may also have capability restrictions, but the relevant capability check and its namespace scope are not shown.

Therefore HostAdminRequired is UNKNOWN rather than YES or NO. NamespaceScopedPrivilege is also UNKNOWN because no complete namespace-scoped trigger chain is established. The issue is not directly remotely reachable through RDMA network traffic. It requires concurrent local control-plane operations and an RDMA-capable environment.

4. Primitive and severity interpretation

The exact primitive is a lifetime mismatch in DMAH destruction. The DMAH remains published in RDMA restrack while device-specific dealloc_dmah processing may already have freed internal vendor resources. A concurrent netlink resource-tracking user may obtain the still-published DMAH and access state whose lifetime has ended.

This is an active structured-object lifetime bug, but the visible stale-use path is associated with destruction and resource tracking. It is not a demonstrated controlled reclaim, arbitrary read or write, callback invocation, repeated refcount mutation, or authorization bypass.

This is CLASS_B because a real UAF or equivalent post-lifetime access is directly implied by the patch. The demonstrated practical consequence is at least a possible kernel fault or local denial of service. Confidentiality, integrity, privilege escalation, and controlled kernel memory corruption remain speculative because the patch does not show attacker-controlled replacement of released vendor resources or a useful post-free field consumption path.

ImportantCandidate is NO because the currently visible evidence is consistent with a constrained teardown-related UAF whose demonstrated leverage beyond crash remains unresolved but weak. Manual review is still recommended because affected vendor dealloc_dmah implementations and netlink resource-tracking consumers determine whether released internal resources are merely observed or actively dereferenced in a more exploitable manner.

AutoDowngradeAllowed is YES under the supplied evidence because no controlled reuse, second lifetime mutation, callback path, security-boundary bypass, or other strong unresolved exploitation primitive is established. This conclusion should be revisited if a vendor driver exposes attacker-influenced DMAH resource contents or if the netlink path dereferences released vendor pointers in a nontrivial way.

5. One-sentence report phrase

A race in RDMA DMAH teardown can leave a DMAH reachable through the restrack netlink path after vendor-specific resources have been released, potentially causing a local kernel use-after-free and denial of service.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Review the relevant RDMA vendor dealloc_dmah implementations and restrack netlink handlers to determine whether the stale path can consume freed attacker-influenced resource state beyond a crash-only dereference.

7. Call-site confidence

Call-site confidence: medium

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

Patch: RDMA/core: Fix potential use after free in uverbs_free_dmah() [ Upstream
Commit: 8b22722f45a29a7c0900b1d4d0bc5da5492ece10
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8b22722f45a29a7c0900b1d4d0bc5da5492ece10

Changed files:
  drivers/infiniband/core/uverbs_std_types_dmah.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=8b22722f45a29a7c0900b1d4d0bc5da5492ece10

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

The original Linux kernel CVE announcement for CVE-2026-93267 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93267

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:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 5.8

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: unknown
  Paranoid ActionableScore: 4

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: NO
Published priority for this report (same as in Subject): MODERATE REGULAR

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).