[CVE-2026-68141][MODERATE REGULAR] net/af_iucv: fix NULL deref in afiucv_hs_callback_syn()

[CVE-2026-68141][MODERATE REGULAR] net/af_iucv: fix NULL deref in afiucv_hs_callback_syn()

[AL-KERNEL]

CVE: CVE-2026-68141
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: net/af_iucv: fix NULL deref in afiucv_hs_callback_syn()
Commit: 8bb111f87ded6acb9837ec9b45d6f02cda94c51f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8bb111f87ded6acb9837ec9b45d6f02cda94c51f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68141
Analysis date: Mon, 10 Aug 2026 15:11:09 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like, manual review recommended due adjacent-network kernel crash
Manual review required: YES

Summary:
A NULL pointer dereference in the AF_IUCV HiperSockets SYN callback can let an adjacent peer crash the kernel when child socket allocation fails and the refusal path calls iucv_sock_kill on a NULL socket.

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

The original Linux kernel CVE announcement for CVE-2026-68141 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68141

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-2026-68141	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';**CWE-476;CWE-703;CWE-754;BEST CVSS score: '5.3';DESCR 'A NULL pointer dereference in the AF_IUCV HiperSockets SYN callback can occur when the child socket allocation fails and nsk remains NULL. The connection refused path then calls iucv_sock_kill on the NULL child socket, which dereferences the socket pointer and can crash the kernel. For the CVSS the PR:N is used because an attacker does not need local privileges on the victim if the AF_IUCV HiperSockets endpoint is reachable. The attack is adjacent network rather than general Internet reachable because HiperSockets is normally limited to IBM Z or s390x internal virtual networking environments. AC:H is used because reliable triggering depends on the GFP_ATOMIC allocation failure condition. Impact is denial of service only via kernel crash.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like, manual review recommended due adjacent-network kernel crash (with actual score 2)	YES	NULLPTR SIMPLEFIX LINUS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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

ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like, manual review recommended due adjacent-network kernel crash**::

## 2. Signal breakdown

* Remote reachable / network-triggerable: +2
  AF_IUCV HiperSockets can be triggered by a peer over an adjacent IBM Z / s390x internal virtual networking path, not by the public Internet.
* Reliable kernel crash / strong DoS: +1
  If `nsk == NULL`, `iucv_sock_kill(nsk)` dereferences a NULL socket pointer and can crash the kernel.
* Hard or unreliable condition required: -1
  Reliable triggering depends on `GFP_ATOMIC` child socket allocation failure or specific refusal-path conditions.
* Rare and difficult-to-reach subsystem/configuration: -1
  AF_IUCV HiperSockets is platform-specific and normally limited to IBM Z / s390x deployments.
* No generic memory corruption: +0
  The primitive is a NULL pointer dereference, not UAF, double-free, OOB write, type confusion, or refcount takeover.
* No confidentiality or integrity impact: +0
  The patch and call path support DoS only.

Paranoid score raises the result to 2 by treating the adjacent-network crash path as worth retaining for manual triage, but still does not upgrade it to memory corruption or LPE.

## 3. Reachability analysis

A peer that can reach the AF_IUCV HiperSockets listener may trigger the vulnerable SYN callback path. The attacker does not need local privileges on the victim, but the path is adjacent-network scoped and depends on IBM Z / s390x HiperSockets configuration.

Namespaces and containers are not the main factor here. Exposure depends more on whether AF_IUCV HiperSockets is enabled and whether an attacker-controlled peer can communicate with the endpoint.

The path is not a broad default Internet-facing kernel networking path. Realistic exploitation requires a configured HiperSockets environment plus allocation-failure or refusal-path conditions.

Call-site confidence: high, because the patch shows the direct caller and the exact NULL dereference path.

## 4. Severity interpretation

This behaves like an ordinary Moderate / Low-like adjacent-network DoS. It is not an Important-class memory corruption issue.

The theoretical impact is a kernel crash. The realistic evidence does not show attacker-controlled reclaim, stale object reuse, write-after-free, callback control, arbitrary write, information disclosure, or privilege escalation.

## 5. One-sentence report phrase

A NULL pointer dereference in the AF_IUCV HiperSockets SYN callback can let an adjacent peer crash the kernel when child socket allocation fails and the refusal path calls iucv_sock_kill on a NULL socket.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: adjacent-network reachable kernel crash in a niche subsystem. It should not be treated as Important without additional evidence, but it is worth manual confirmation of product exposure to AF_IUCV HiperSockets.

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

Patch: net/af_iucv: fix NULL deref in afiucv_hs_callback_syn()
Commit: 8bb111f87ded6acb9837ec9b45d6f02cda94c51f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8bb111f87ded6acb9837ec9b45d6f02cda94c51f

Commit description:

afiucv_hs_callback_syn() allocates the child socket with GFP_ATOMIC.
If the allocation fails, nsk is NULL.

The connection-refused path is entered when the listen state check
fails, the accept backlog is full, or nsk is NULL. The code
unconditionally calls iucv_sock_kill(nsk) in that path.

iucv_sock_kill() does not accept a NULL socket pointer and immediately
dereferences sk via sock_flag(sk, SOCK_ZAPPED). When nsk is NULL,
calling iucv_sock_kill(nsk) results in a NULL pointer dereference.

Only call iucv_sock_kill() when a child socket was successfully
allocated.

Fixes: 3881ac4 ("af_iucv: add HiperSockets transport")
Cc: stable@vger.kernel.org
Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
Signed-off-by: Hidayath Khan <hidayath@linux.ibm.com>
Link: https://patch.msgid.link/20260709191732.124092-1-hidayath@linux.ibm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/iucv/af_iucv.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=8bb111f87ded6acb9837ec9b45d6f02cda94c51f

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

The original Linux kernel CVE announcement for CVE-2026-68141 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68141

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: Not available
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.3

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: 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).