[CVE-2026-53233][MODERATE 7.0] netdev: fix double-free in netdev_nl_bind_rx_doit() [ Upstream

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

CVE: CVE-2026-53233
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: netdev: fix double-free in netdev_nl_bind_rx_doit() [ Upstream
Commit: e055ca9205d3eb6aec3e5fe4ecc18abbbf18c599
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e055ca9205d3eb6aec3e5fe4ecc18abbbf18c599
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53233
Analysis date: Thu, 25 Jun 2026 21:04:41 -0400
ActionableScore: 6
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A local netdev generic netlink error path can double-free a reply skb because `genlmsg_reply()` consumes the skb even on failure, allowing a CAP_NET_ADMIN-level or delegated network-management attacker to trigger kernel memory corruption and likely DoS, with privilege escalation requiring manual review.

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

The original Linux kernel CVE announcement for CVE-2026-53233 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53233

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-2026-53233	MODERATE	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-415;*CWE-672;CWE-703;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.8';DESCR 'A double-free can occur in netdev_nl_bind_rx_doit() because genlmsg_reply() consumes the reply skb even when it returns an error. If the error path then treats the same skb as still owned by the caller, the reply buffer may be freed a second time and corrupt kernel memory. A local attacker can influence this path by causing genlmsg_reply() to fail, for example with a full receive buffer, after invoking the netdev generic netlink bind operation. For the CVSS the PR:L is used in the paranoid score because the operation normally needs network administration capability, but delegated CAP_NET_ADMIN, container root, or a service account can make the practical attacker privilege closer to low than full host administrator. The issue is not directly network reachable and requires local access to the netlink control interface. Impact is at least local denial of service via kernel crash, and in the worst case may allow confidentiality or integrity impact because double-free is a kernel memory corruption primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5)  SKIP CVE-2026-53233  SKIP The Fixes patch not applied yet, so unlikely that actual: 170aafe35cb98e0f3fbacb446ea86389fbce22ea YES  NO NO unknown 	MAYBE	REMOTE DANGER ERRORPATH UAF KPANIC MEMORY  KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7	-	-	checked

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

ActionableScore=6
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 6
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Memory corruption, Strong corruption primitive: +2
  `genlmsg_reply()` consumes `rsp` even on error, while the old error path could later free the same skb again via `nlmsg_free(rsp)`. This is a real kernel double-free.

* Real lifetime corruption: +1
  The bug is specifically an ownership and lifetime mismatch for an skb.

* Reliable kernel crash / strong DoS: +1
  Double-free of skb memory can realistically lead to allocator corruption, warning, BUG, or kernel crash.

* Privileged kernel/device-management memory corruption path: +1
  The affected operation is netdev dma-buf binding through netdev generic netlink, a trusted network device management path.

* Requires CAP_NET_ADMIN or similar in typical deployments: -2
  This operation is expected to require network administration privileges on the host or in an authorized namespace.

Conservative total: 4

Paranoid additional or adjusted signals:

* Weak LPE concern: +1
  Double-free is a memory corruption primitive and should not be treated as DoS-only, even though the patch does not demonstrate a controlled reclaim or arbitrary write primitive.

* Local high-control netlink/device API concern: +1
  The trigger is a local generic netlink control path where user-controlled request state and socket receive-buffer behavior can influence the failure path.

* Privilege penalty reduced: +0 instead of -2 in the paranoid interpretation
  CAP_NET_ADMIN may be delegated to container root, network-management services, or reduced-capability accounts. This is not equivalent to full host root in practical triage.

Paranoid total: 6

Not counted:

* Remote reachable: +0
  This is not a packet-processing or remotely triggerable network path.

* Strong LPE plausibility: +0
  The patch supports double-free memory corruption, but does not show a demonstrated reclaim, arbitrary write, controlled overwrite, or reliable object-confusion primitive.

## 3. Reachability analysis

The bug is triggered locally through the netdev generic netlink bind operation. In normal host deployments this likely requires CAP_NET_ADMIN or equivalent network-device management rights. However, CAP_NET_ADMIN is commonly delegated to containers, network agents, or service accounts, so the practical privilege boundary may be lower than full host administrator.

The failure condition is unusual but user-influenceable: the commit explicitly mentions `genlmsg_reply()` failures such as calling the kernel with an already full receive buffer. This makes the bug more actionable than a purely theoretical cleanup issue, but still not remotely reachable through ordinary network traffic.

## 4. Severity interpretation

This behaves like an actionable Moderate issue with Important-candidate properties. The realistic impact is local kernel crash or allocator corruption after a double-free. The theoretical impact includes privilege escalation because double-free is a real kernel memory corruption class, but the patch does not prove a reliable exploitation primitive.

Conservative handling should not auto-close this as a routine Moderate because the primitive is lifetime corruption in core networking management code. Paranoid handling should keep it in manual review due to the double-free and possible delegated CAP_NET_ADMIN reachability.

## 5. One-sentence report phrase

A local netdev generic netlink error path can double-free a reply skb because `genlmsg_reply()` consumes the skb even on failure, allowing a CAP_NET_ADMIN-level or delegated network-management attacker to trigger kernel memory corruption and likely DoS, with privilege escalation requiring manual review.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a real kernel double-free in an skb lifetime path. Even though typical triggering requires CAP_NET_ADMIN and the demonstrated impact is likely DoS, the memory corruption primitive and possible delegated-capability reachability make auto-closure unsafe.

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

Patch: netdev: fix double-free in netdev_nl_bind_rx_doit() [ Upstream
Commit: e055ca9205d3eb6aec3e5fe4ecc18abbbf18c599
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e055ca9205d3eb6aec3e5fe4ecc18abbbf18c599

Changed files:
  net/core/netdev-genl.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=e055ca9205d3eb6aec3e5fe4ecc18abbbf18c599

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

The original Linux kernel CVE announcement for CVE-2026-53233 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53233

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:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.8

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: 4
  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).