[CVE-2026-53227][MODERATE REGULAR] net: openvswitch: fix possible kfree_skb of ERR_PTR [ Upstream

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

CVE: CVE-2026-53227
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: net: openvswitch: fix possible kfree_skb of ERR_PTR [ Upstream
Commit: e248fb2e680deb2bd37bac551b72638fe4938a76
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e248fb2e680deb2bd37bac551b72638fe4938a76
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53227
Analysis date: Thu, 25 Jun 2026 09:26:01 -0400
ActionableScore: 2
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Borderline manual-review candidate
Manual review required: NO

Summary:
Open vSwitch flow update error handling could leave an `ERR_PTR` in `reply` after skb allocation failure, causing the cleanup path to call `kfree_skb()` on an invalid pointer and crash the kernel when reachable through privileged or delegated OVS control-plane access.

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

The original Linux kernel CVE announcement for CVE-2026-53227 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53227

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: NO

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-2026-53227	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:N/I:N/A:H';CWE-763;CWE-754;CWE-703;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'Open vSwitch flow update error handling can leave reply as ERR_PTR when reply skb allocation fails after ovs_mutex is already locked. The common cleanup path may then call kfree_skb on this invalid error pointer, causing a kernel crash. For the CVSS the PR:L is used in the paranoid score because delegated CAP_NET_ADMIN, container root, or an OVS management service account may be enough to reach the Open vSwitch generic netlink control path in some deployments. The issue is not directly network reachable through packet traffic and requires local control plane access plus an allocation failure condition. Impact is denial of service via kernel crash, with no clear confidentiality or integrity impact because the invalid pointer is an ERR_PTR value rather than an attacker controlled kernel object pointer.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Borderline manual-review candidate (with actual score 1)	YES	LOCK UAF SKB LINUS  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=2
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Borderline manual-review candidate**::

## 2. Signal breakdown

Conservative scoring:

* Weak/indirect corruption candidate: +1. `reply` can hold an `ERR_PTR` and the cleanup path can pass it to `kfree_skb()`, but this is an invalid error pointer rather than an attacker-controlled object pointer.
* Reliable kernel crash / strong DoS: +1. If the path is reached, freeing an `ERR_PTR` is expected to cause an Oops or panic.
* Hard or unreliable condition: -1. Triggering requires the specific cleanup path plus allocation failure after `ovs_mutex` is locked.
* Requires CAP_NET_ADMIN in typical deployments: -2. Open vSwitch flow updates through the generic netlink control plane normally require administrative network privileges.
* Broad/default/common exposure: +1 not applied conservatively. Open vSwitch is common in virtualized and cloud deployments, but it is not a default generic network receive path.

Paranoid scoring:

* Same +1 weak corruption and +1 crash signals.
* The CAP_NET_ADMIN penalty is relaxed in delegated environments where container root, a reduced-capability OVS manager, or a service account can reach the OVS control plane.
* No LPE, confidentiality, or integrity points are awarded because the pointer is an `ERR_PTR`, not a controllable freed object, reclaim primitive, callback target, or arbitrary write.

## 3. Reachability analysis

The bug is triggered through the Open vSwitch control plane, specifically a flow set operation in `ovs_flow_cmd_set()`. It is not reachable by ordinary packet traffic alone and is not a remote network parser issue.

In typical host deployments, the attacker needs CAP_NET_ADMIN or equivalent control over OVS configuration. Namespaces or containerized environments can lower the practical barrier if OVS management is delegated to container root, a network-management service, or a reduced-privilege account. Reliable triggering also depends on forcing or encountering an allocation failure at the relevant point, so exploitation is less straightforward than a normal local ioctl/netlink crash.

## 4. Severity interpretation

This behaves more like an ordinary Moderate or borderline manual-review issue than an Important-class vulnerability. The bug is a kernel invalid-free style cleanup error, but the freed value is an `ERR_PTR` error encoding and does not provide an evident attacker-controlled payload, object replacement, UAF reclaim, type confusion, or write primitive.

Realistic impact is local denial of service through kernel crash. Theoretical memory-corruption concern exists only in the broad sense that an invalid pointer is passed to a free routine, but the patch context does not support confidentiality impact, integrity impact, or privilege escalation.

## 5. One-sentence report phrase

Open vSwitch flow update error handling could leave an `ERR_PTR` in `reply` after skb allocation failure, causing the cleanup path to call `kfree_skb()` on an invalid pointer and crash the kernel when reachable through privileged or delegated OVS control-plane access.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: the issue is probably DoS-only and low-actionability in standard deployments, but it is still an invalid free pattern in a kernel networking control path and may matter in environments where OVS control is delegated to less-than-full-root actors.

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

Patch: net: openvswitch: fix possible kfree_skb of ERR_PTR [ Upstream
Commit: e248fb2e680deb2bd37bac551b72638fe4938a76
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e248fb2e680deb2bd37bac551b72638fe4938a76

Changed files:
  net/openvswitch/datapath.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=e248fb2e680deb2bd37bac551b72638fe4938a76

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

The original Linux kernel CVE announcement for CVE-2026-53227 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53227

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:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 0
  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).