[CVE-2026-53005][MODERATE 7.0] af_unix: Drop all SCM attributes for SOCKMAP. [ Upstream

[CVE-2026-53005][MODERATE 7.0] af_unix: Drop all SCM attributes for SOCKMAP. [ Upstream

[AL-KERNEL]

CVE: CVE-2026-53005
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: af_unix: Drop all SCM attributes for SOCKMAP. [ Upstream
Commit: b34a1d83c74a124c968b5adb25c809db3e2eb86a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b34a1d83c74a124c968b5adb25c809db3e2eb86a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53005
Analysis date: Wed, 24 Jun 2026 14:21:55 -0400
ActionableScore: 6
ActionableScore lower bound: 3
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
AF_UNIX SOCKMAP redirect can hide SCM file descriptor state from AF_UNIX garbage collection, leading to stale socket lifetime assumptions and a slab use-after-free in `unix_del_edges()`, with realistic local DoS impact and potential manual-review concern for LPE in delegated BPF or SOCKMAP environments.

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

The original Linux kernel CVE announcement for CVE-2026-53005 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53005

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-2026-53005	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-416;*CWE-664;*CWE-772;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'AF_UNIX with SOCKMAP can hide skb objects carrying SCM file descriptor state from the AF_UNIX garbage collector because the psock ingress queue is not inspected by that GC path. This breaks the assumption that unix_edge successor objects remain alive during Tarjan based GC traversal and can lead to a slab use-after-free in unix_del_edges. For the CVSS the PR:L is used in the paranoid score because a local actor with delegated BPF or network administration capability, container root, or a service account controlling SOCKMAP setup may be sufficient in practical deployments. The issue is not network reachable by packet traffic and requires local code execution or local control over socket and SOCKMAP setup. Impact is at least a local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to kernel use-after-free, so it should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5)	YES	REMOTE READ LOCK LEAK UAF SKB HARDWARE  KPANIC INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS	NO	NO	checked

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

ActionableScore=6
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: **3**
* Paranoid score: **6**
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* **Memory corruption, weak primitive: +1**. The patch includes a concrete KASAN `slab-use-after-free` in `unix_del_edges()`, but the observed access is a stale read and the patch does not show attacker-controlled reclaim, overwrite, callback dispatch, or type confusion.
* **Real lifetime corruption: +1**. SCM state and inflight AF_UNIX sockets can survive in a `psock->ingress_skb` queue that AF_UNIX GC cannot inspect, creating a stale lifetime relationship.
* **Reliable kernel crash / strong DoS: +1**. The KASAN trace shows a real UAF during workqueue processing, and without KASAN this can plausibly become an Oops or panic.
* **Requires CAP/BPF/SOCKMAP setup in typical deployments: -2**. Reliable triggering normally requires SOCKMAP/BPF control, usually restricted by `CAP_NET_ADMIN`, `CAP_BPF`, or equivalent policy.
* **Local high-control kernel data-plane API: +1**. SOCKMAP/BPF plus AF_UNIX sockets and SCM_RIGHTS provide relatively fine control over socket, skb, and file-descriptor lifetime interactions.
* **Broad local subsystem exposure: +1**. AF_UNIX is a common local IPC subsystem, although the vulnerable interaction specifically requires SOCKMAP.

Paranoid-only interpretation:

* **Weak LPE concern: +1**. The bug is an explicit kernel UAF involving AF_UNIX socket GC state and stale `unix_edge.successor` assumptions. No exploit primitive is demonstrated, but this class deserves manual review.
* **Reduced privilege interpretation instead of full admin penalty**. In containerized or delegated environments, a service account or container root with BPF or network administration rights may be enough to set up SOCKMAP without being equivalent to full host root.

## 3. Reachability analysis

The issue is locally reachable through AF_UNIX sockets combined with SOCKMAP redirect behavior and SCM_RIGHTS or other SCM state. It is **not network reachable by packet traffic**.

In typical hardened deployments, SOCKMAP setup is not available to an ordinary unprivileged user because BPF and sockmap operations are capability-gated. However, namespaces, container root, delegated `CAP_NET_ADMIN`, BPF-enabled service accounts, or less restrictive BPF policy may lower the practical privilege requirement from full host root to a reduced local privilege context.

The path is not a default remote attack surface, but AF_UNIX is common and SOCKMAP/BPF is a high-risk local kernel data-plane interface when available.

## 4. Severity interpretation

This is stronger than an ordinary Moderate because the patch documents a real `slab-use-after-free`, not just a leak or accounting bug. Conservative treatment is still bounded because the demonstrated primitive is a stale read during GC cleanup, with no shown attacker-controlled reclaim, write-after-free, object replacement, or callback hijack.

Realistically, the demonstrated impact is local DoS through kernel crash. Theoretical LPE concern exists because this is a kernel UAF in socket lifetime and GC logic, but the patch does not prove a reliable privilege escalation primitive. Therefore it should be treated as **Actionable Moderate at minimum**, with **Important-candidate manual review** if SOCKMAP/BPF is available to reduced-privilege users.

## 5. One-sentence report phrase

AF_UNIX SOCKMAP redirect can hide SCM file descriptor state from AF_UNIX garbage collection, leading to stale socket lifetime assumptions and a slab use-after-free in `unix_del_edges()`, with realistic local DoS impact and potential manual-review concern for LPE in delegated BPF or SOCKMAP environments.

## 6. Manual review recommendation

**MANUAL CHECK REQUIRED**

Reason: the patch contains an explicit KASAN `slab-use-after-free` in AF_UNIX GC involving socket and SCM lifetime state. Even though practical exploitation beyond DoS is not demonstrated, kernel UAF plus SOCKMAP/BPF reachability is enough to require manual review rather than auto-close.

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

Patch: af_unix: Drop all SCM attributes for SOCKMAP. [ Upstream
Commit: b34a1d83c74a124c968b5adb25c809db3e2eb86a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b34a1d83c74a124c968b5adb25c809db3e2eb86a

Changed files:
  net/unix/garbage.c
  lib/dump_stack.c
  mm/kasan/report.c
  include/net/scm.h
  net/unix/af_unix.c
  include/linux/skbuff.h
  kernel/workqueue.c
  kernel/kthread.c
  arch/x86/kernel/process.c
  arch/x86/entry/entry_64.S
  mm/kasan/common.c
  mm/slub.c
  net/core/sock.c
  net/socket.c
  arch/x86/entry/syscall_64.c
  mm/kasan/generic.c
  include/net/sock.h

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=b34a1d83c74a124c968b5adb25c809db3e2eb86a

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

The original Linux kernel CVE announcement for CVE-2026-53005 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53005

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: 3
  Paranoid ActionableScore: 6

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).