[CVE-2026-74465][MODERATE 7.0] net: openvswitch: fix potential UAF on meter attach failure

[CVE-2026-74465][MODERATE 7.0] net: openvswitch: fix potential UAF on meter attach failure

[AL-KERNEL]

CVE: CVE-2026-74465
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: net: openvswitch: fix potential UAF on meter attach failure
Commit: 0310d1fa7f9debd0d89629e9f14c7975a47eaa9a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0310d1fa7f9debd0d89629e9f14c7975a47eaa9a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74465
Analysis date: Sat, 15 Aug 2026 15:39:09 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
Open vSwitch meter attachment can publish a new meter to RCU readers before all failure checks complete, allowing a custom local OVS uAPI client with network administration privileges to race an attach failure with packet execution and trigger a slab use after free in `ovs_meter_execute`.

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

The original Linux kernel CVE announcement for CVE-2026-74465 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74465

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-2026-74465	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	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-362;*CWE-672;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'Open vSwitch meter attachment can expose a newly allocated meter to RCU readers before attach_meter has reached a point where it cannot fail. If a later failure path removes the meter and ovs_meter_cmd_set frees it with kfree, a concurrent packet execution path can still dereference the stale meter in ovs_meter_execute, producing a slab use after free. For the CVSS the PR:L is used for the paranoid score because triggering requires local code or a process with access to the Open vSwitch netlink uAPI, commonly CAP_NET_ADMIN or delegated network administration rather than full host root. The issue is not directly reachable by ordinary network packets alone and usually needs a custom local control application that creates a meter and races packet execution. Impact is at least local denial of service via kernel crash. In the worst defensible case, the RCU use after free may allow broader confidentiality or integrity impact and should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 4)	YES	READ DANGER NOMEMCHK UAF HARDWARE  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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

ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Memory corruption, weak race-UAF primitive: +1. The patch and KASAN trace show a real slab-use-after-free in `ovs_meter_execute`, but only a stale read is demonstrated.
* Real lifetime corruption: +1. A meter becomes visible to RCU readers and is later freed with plain `kfree` without waiting for readers.
* Reliable kernel crash / strong DoS: +1. KASAN shows a concrete UAF crash path through packet action execution.
* Hard or timing-dependent race: -1. Triggering requires overlap between meter attach failure and concurrent packet execution.
* Requires CAP_NET_ADMIN or OVS control-plane access in typical deployments: -1 to -2. Full penalty is softened because delegated network administration, container root, or OVS service contexts may be weaker than full host root.

Paranoid additions:

* Generic memory corruption concern: +1 upgrade relative to conservative. Although no reclaim or write primitive is shown, this is an RCU-visible UAF in a packet-processing path and was reported as ZDI-CAN-31642.
* Open vSwitch packet-processing exposure in relevant deployments: +1. OVS is common in virtualization, container, and cloud networking, even though it is not a default Internet-facing kernel path.

No remote-reachable bonus is applied. Ordinary network packets alone are not enough without the local OVS uAPI/control-plane setup.

## 3. Reachability analysis

The bug is triggerable by a custom local application using the Open vSwitch uAPI, not by normal `ovs-vswitchd` behavior according to the commit message. In typical host deployments this requires `CAP_NET_ADMIN` or equivalent OVS datapath control privileges, so it is not a plain unprivileged local bug. Namespace or container delegation can materially change the risk because a reduced-capability root, container root, or service account with OVS control access may be able to reach the vulnerable path without being equivalent to full host root.

The path is not directly network reachable. However, once the control-plane operation exposes and frees the meter incorrectly, the stale object is consumed from the OVS packet execution path.

Call-site confidence: high. The commit includes the failing call trace, allocation path, free path, and dereference path.

## 4. Severity interpretation

This is more than an ordinary Moderate because it is a demonstrated UAF, not merely a warning or validation cleanup. Realistic impact is local kernel crash / DoS under a custom OVS uAPI trigger and race timing. Practical LPE is not demonstrated because there is no shown attacker-controlled reclaim, write-after-free, callback control, or type confusion primitive.

For conservative triage it fits Borderline / manual review recommended. For paranoid triage it should be treated as Actionable Moderate at minimum and a Strong Important candidate for environments where OVS control is delegated to less-than-full-root actors.

## 5. One-sentence report phrase

Open vSwitch meter attachment can publish a new meter to RCU readers before all failure checks complete, allowing a custom local OVS uAPI client with network administration privileges to race an attach failure with packet execution and trigger a slab use after free in `ovs_meter_execute`.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED.

Reason: the patch fixes a demonstrated RCU-visible UAF in a packet-processing subsystem, and the real-world severity depends strongly on whether OVS control-plane access is delegated to containers, service accounts, or reduced-capability administrators.

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

Patch: net: openvswitch: fix potential UAF on meter attach failure
Commit: 0310d1fa7f9debd0d89629e9f14c7975a47eaa9a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0310d1fa7f9debd0d89629e9f14c7975a47eaa9a

Commit description:

While attaching a newly created meter attach_meter() function makes
the new meter visible to other CPUs but can still fail afterwards.
On failure, it detaches the meter back and returns an error.

However, this is an unexpected behavior for the ovs_meter_cmd_set()
that uses a plain kfree(meter) on attach failure without waiting for
RCU readers to stop using it, assuming it was never visible.

This is never a problem for ovs-vswitchd as it always creates meters
before creating any flows that use them.  But the UAF can be triggered
with a custom application using uAPI:

 BUG: KASAN: slab-use-after-free in ovs_meter_execute (net/openvswitch/meter.c:653)
 Read of size 8 at addr ffff88810d152650 by task meter/2508

 Call Trace:
  ovs_meter_execute (net/openvswitch/meter.c:653)
  do_execute_actions (net/openvswitch/actions.c:1407)
  ovs_execute_actions (net/openvswitch/actions.c:1584)
  ovs_packet_cmd_execute (net/openvswitch/datapath.c:703)
  ...
  netlink_sendmsg (af_netlink.c:1900)

 Allocated by task 2519:
  __kasan_kmalloc (mm/kasan/common.c:398 mm/kasan/common.c:415)
  ovs_meter_cmd_set (net/openvswitch/meter.c:422)
  ...
  netlink_sendmsg (af_netlink.c:1900)

 Freed by task 2519:
  kfree (mm/slub.c:2705 mm/slub.c:6405 mm/slub.c:6720)
  ovs_meter_cmd_set (net/openvswitch/meter.c:479)
  ...
  netlink_sendmsg (af_netlink.c:1900)

Fix that by making sure attach_meter() doesn't make the meter visible
until all the checks are done and the function can't fail anymore.

This also makes sure the "hash" value is calculated after the potential
re-sizing of the table.

Reported by Trend Micro's Zero Day Initiative as ZDI-CAN-31642.

Fixes: c7c4c44 ("net: openvswitch: expand the meters supported number")
Cc: stable@vger.kernel.org
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
Reviewed-by: Eelco Chaudron <echaudro@redhat.com>
Link: https://patch.msgid.link/20260727121022.198461-1-i.maximets@ovn.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/openvswitch/meter.c
  net/openvswitch/actions.c
  net/openvswitch/datapath.c
  mm/kasan/common.c
  mm/slub.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=0310d1fa7f9debd0d89629e9f14c7975a47eaa9a

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

The original Linux kernel CVE announcement for CVE-2026-74465 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74465

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: 5

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 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).