[CVE-2026-63860][MODERATE REGULAR] RDMA/core: Prefer NLA_NUL_STRING [ Upstream

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

CVE: CVE-2026-63860
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: RDMA/core: Prefer NLA_NUL_STRING [ Upstream
Commit: fcd07d3b8ee7a39b344d73aed69c1a68cd9eacdf
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fcd07d3b8ee7a39b344d73aed69c1a68cd9eacdf
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63860
Analysis date: Sun, 19 Jul 2026 11:39:40 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline manual review recommended / ordinary Moderate with OOB-read concern
Manual review required: YES

Summary:
RDMA iWARP Port Mapper netlink attributes used as C strings were not required to be NUL terminated, allowing a local process to trigger an out-of-bounds kernel read with possible limited information exposure or local DoS.

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

The original Linux kernel CVE announcement for CVE-2026-63860 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63860

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-2026-63860	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H';CWE-125;*CWE-20;CWE-170;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L';BEST CVSS score: '6.1';DESCR 'RDMA iWARP Port Mapper netlink attributes were accepted as NLA_STRING even though later code treats them as C strings and passes them to strcmp or percent s style formatting. A local process able to send the relevant RDMA netlink messages can provide a non NUL terminated attribute, causing kernel code to read past the end of the attribute until a zero byte is found. For the CVSS the PR:L is used because triggering requires local code execution or a local process context that can access the netlink interface, not remote network traffic. The issue is not network reachable in the CVSS sense. Impact is mainly local denial of service and possible limited confidentiality exposure from an out-of-bounds read. There is no clear write primitive, UAF, or direct privilege escalation path in this patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended / ordinary Moderate with OOB-read concern (with actual score 3)	YES	SIMPLEFIX NETWORK  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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

ActionableScore=3
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 3
* Final recommended bucket: **Borderline manual review recommended / ordinary Moderate with OOB-read concern**

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1
  A local process able to send the relevant RDMA iWARP Port Mapper netlink messages can provide a non NUL terminated attribute.
* Confidentiality impact plausible: +1
  The attributes are later treated as C strings and passed to strcmp or percent-s style formatting, so a bounded attribute can cause read past the netlink attribute payload until a NUL byte is encountered.

Paranoid additional signal:

* Reliable kernel crash / strong DoS: +1
  Not proven, but a kernel C-string overread can plausibly lead to an Oops, KASAN report, or fault depending on allocation layout and where the unterminated string ends.

Signals not applied:

* No remote reachable signal. This is a local netlink/control-plane path, not packet-triggered RDMA network traffic.
* No privilege escalation signal. The patch shows read past end / missing NUL validation, not UAF, write primitive, refcount takeover, callback control, or type confusion.
* No generic strong memory corruption signal. This is read-only OOB string access, not OOB write or object lifetime corruption.
* No high-control RDMA API bonus. The patch does not show attacker control over allocator layout, object lifetime, DMA mappings, refcounts, or callback targets.

Call-site confidence: medium-high. The commit explicitly states the affected attributes are evaluated as C strings and passed to strcmp, but the full downstream call graph is not included in the provided patch.

## 3. Reachability analysis

The likely trigger is a local process sending malformed RDMA netlink messages to the iWARP Port Mapper path. This is not realistically network-triggerable by remote RDMA traffic alone. Namespace behavior is product-dependent, but this should be treated as PR:L rather than PR:N because local code execution or a local process context is required. Exposure depends on RDMA/iWARP support and whether the relevant kernel module and netlink family are available, so this is not a broad default kernel path.

## 4. Severity interpretation

This behaves like an ordinary Moderate issue with enough OOB-read uncertainty to justify manual review. The realistic impact is limited information exposure or local DoS. The theoretical worst case is a kernel crash from C-string overread, but the patch does not support privilege escalation or arbitrary memory corruption. It should not be treated as an Important candidate without additional evidence of disclosure, crash reliability, or a stronger downstream primitive.

## 5. One-sentence report phrase

RDMA iWARP Port Mapper netlink attributes used as C strings were not required to be NUL terminated, allowing a local process to trigger an out-of-bounds kernel read with possible limited information exposure or local DoS.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: this is not a strong Important candidate, but kernel C-string OOB reads can have context-dependent disclosure or crash behavior, and the patch explicitly mentions strcmp / percent-s style string usage.

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

Patch: RDMA/core: Prefer NLA_NUL_STRING [ Upstream
Commit: fcd07d3b8ee7a39b344d73aed69c1a68cd9eacdf
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fcd07d3b8ee7a39b344d73aed69c1a68cd9eacdf

Changed files:
  drivers/infiniband/core/iwpm_msg.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=fcd07d3b8ee7a39b344d73aed69c1a68cd9eacdf

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

The original Linux kernel CVE announcement for CVE-2026-63860 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63860

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:L/UI:N/S:U/C:L/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H
  The Best / paranoid CVSS score: 6.1

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: 2
  Paranoid ActionableScore: 3

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).