# CVE-2026-74664: net: openvswitch: reallocate update replies for mismatched IDs

> A local attacker can trigger a kernel crash in Open vSwitch by sending crafted flow update requests with mismatched identifiers.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 Aug 2026
- **Updated:** 22 Aug 2026
- **Also known as:** AZL-97154, BELL-CVE-2026-74664, DEBIAN-CVE-2026-74664, GHSA-2jvw-5ch9-j793, UBUNTU-CVE-2026-74664

## What is CVE-2026-74664?

CVE-2026-74664 is a denial of service vulnerability in Linux, published on 22 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

net: openvswitch: reallocate update replies for mismatched IDs

ovs_flow_cmd_new() preallocates the optional reply skb before it takes
ovs_mutex and before it knows which existing flow will be updated.

That is normally fine because the skb is sized from the request flow
identifier.  That identifier also becomes the inserted flow's identifier.
For updates, however, a request with a UFID may miss the UFID lookup and
then fall back to the flow key lookup.  That lookup can legitimately find
an existing key-identified flow.  UFIDs are optional and the flow key is
the primary identifier.

For echoed replies, ovs_flow_cmd_fill_info() writes the matched flow's
identifier, not the request identifier used for the preallocation.  A short
request UFID can therefore leave too little room for the key identifier.
The fill can then fail with -EMSGSIZE and hit the BUG_ON(error < 0) in the
update path.

Once the update target has been resolved, reallocate the reply skb if the
matched flow needs a larger reply than the request identifier allowed.  Do
this before replacing the actions so the request can still fail cleanly if
the rare extra allocation fails.

## Which versions are affected by CVE-2026-74664?


## How do I fix CVE-2026-74664?

Apply the vendor's patch.

## Is CVE-2026-74664 being exploited?

There is no known exploitation of CVE-2026-74664 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74664 and fix it if it is affected.

What it is: CVE-2026-74664 is a denial of service vulnerability in Linux, published on 22 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-74664 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-74664/ (Markdown: https://insights.sbomify.com/CVE-2026-74664/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74664
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74664
- OSV: https://osv.dev/vulnerability/CVE-2026-74664

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74664/
Summaries are generated and may contain mistakes; the official description above is the record.