[CVE-2026-53034][MODERATE 7.0] bpf, sockmap: Fix af_unix null-ptr-deref in proto update [ Upstream

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

CVE: CVE-2026-53034
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: bpf, sockmap: Fix af_unix null-ptr-deref in proto update [ Upstream
Commit: 75b7d3b3f8bd4e59eb3af1b11a43c64c0c2db6f4
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=75b7d3b3f8bd4e59eb3af1b11a43c64c0c2db6f4
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53034
Analysis date: Thu, 25 Jun 2026 15:12:56 -0400
ActionableScore: 7
ActionableScore lower bound: 3
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
An AF_UNIX sockmap race can let BPF update a socket after `sk_state` becomes established but before `unix_peer(sk)` is assigned, causing a local kernel NULL pointer dereference and raising a related UAF concern that requires manual review.

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

The original Linux kernel CVE announcement for CVE-2026-53034 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53034

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-53034	MODERATE	CHECK	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-476;CWE-362;*CWE-416;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'An af_unix sockmap race can call unix_stream_bpf_update_proto while unix_stream_connect has already set sk_state to TCP_ESTABLISHED but has not assigned unix_peer(sk) yet. The sockmap update path treats the socket state as valid and then dereferences a NULL peer through sock_hold, causing a kernel NULL-pointer dereference and local DoS. For the CVSS the PR:L is used because triggering requires local code execution with access to BPF sockmap update paths or BPF programs that can update sockmaps, but it does not require full host administrator control in delegated BPF or container like environments. The issue is not directly network reachable and is triggered through local BPF and socket operations rather than packet traffic. The base impact is kernel crash only, but the race context and the commit text also discuss a closely related poorly timed close path that may lead to use-after-free, so the paranoid impact is treated as possible C:H/I:H/A:H and requires manual review.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5) 	MAYBE	REMOTE LOCK DEADLOCK NULLPTR BPF RACE UAF HARDWARE TEST  KPANIC INCREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN5	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=7
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged or low-privileged trigger: +1
  Triggering requires local execution with access to BPF sockmap update paths or BPF programs. This is PR:L in practical CVSS terms, not remote.
* Local high-control kernel data-plane API: +1
  BPF sockmap is a rich local kernel API where user-controlled programs and maps can shape socket update timing.
* Reliable kernel crash / strong DoS: +1
  The demonstrated failure is a kernel NULL pointer dereference in `unix_stream_bpf_update_proto()`.
* Hard or unreliable race / special timing required: -1
  The issue depends on racing `unix_stream_connect()` between `sk_state = TCP_ESTABLISHED` and `unix_peer(sk) = newsk`.

Conservative subtotal: 3

Paranoid additional signals:

* Generic memory corruption, strong corruption primitive: +2
  The commit text explicitly discusses a related poorly timed `close()` path that may lead to use-after-free.
* Real lifetime corruption: +1
  The related scenario involves `unix_peer(sk)` being cleared and `sock_put()` racing with later `sock_hold(sk_pair)`.
* Weak LPE concern: +1
  A UAF in a BPF and socket lifetime path may be privilege-escalation relevant, but no reliable reclaim or controlled overwrite primitive is demonstrated in this patch.
* Availability impact realistic: +1
  The demonstrated crash is host-kernel level and directly affects system availability.

Paranoid subtotal: 7

## 3. Reachability analysis

The bug is locally reachable through BPF sockmap update paths racing with AF_UNIX stream socket connection setup. It is not directly network reachable because the trigger is local BPF and socket control-plane activity, not packet input.

In typical hardened deployments, BPF program loading and some sockmap operations may require elevated capabilities such as CAP_BPF, CAP_NET_ADMIN, or equivalent policy permissions. However, delegated BPF environments, containers with selected capabilities, tracing setups, or service accounts with BPF access can make this closer to PR:L than full PR:H.

The affected components are common kernel subsystems, AF_UNIX and BPF sockmap, but the exact trigger requires a nontrivial race and BPF availability. Realistic exploitation for DoS is plausible. Practical privilege escalation is not proven by this patch, but the explicitly mentioned UAF follow-up concern makes this unsuitable for auto-close.

## 4. Severity interpretation

Conservatively, this behaves like an actionable local Moderate issue: a local BPF/sockmap race causes a kernel NULL pointer dereference and DoS.

Paranoid interpretation is stronger because the commit message itself states that the NULL check is insufficient for a related close-race scenario that may lead to use-after-free. That moves the issue into manual-review territory as a Strong Important candidate, even though the demonstrated patch only fixes the NULL dereference path and does not prove a controlled UAF exploitation primitive.

## 5. One-sentence report phrase

An AF_UNIX sockmap race can let BPF update a socket after `sk_state` becomes established but before `unix_peer(sk)` is assigned, causing a local kernel NULL pointer dereference and raising a related UAF concern that requires manual review.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a race in a BPF sockmap path with demonstrated kernel crash and an explicitly documented related use-after-free concern. The base issue is DoS, but the lifetime-race context is security-sensitive enough to require human triage.

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

Patch: bpf, sockmap: Fix af_unix null-ptr-deref in proto update [ Upstream
Commit: 75b7d3b3f8bd4e59eb3af1b11a43c64c0c2db6f4
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=75b7d3b3f8bd4e59eb3af1b11a43c64c0c2db6f4

Changed files:
  net/unix/unix_bpf.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=75b7d3b3f8bd4e59eb3af1b11a43c64c0c2db6f4

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

The original Linux kernel CVE announcement for CVE-2026-53034 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53034

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: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: 3
  Paranoid ActionableScore: 7

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).