# CVE-2023-53843: net: openvswitch: reject negative ifindex

> A local attacker can cause a denial of service in the Linux kernel Open vSwitch module by providing a negative interface index.

- **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:** 9 Dec 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2023-53843, DEBIAN-CVE-2023-53843, GHSA-26x8-4cm5-whjx, UBUNTU-CVE-2023-53843

## What is CVE-2023-53843?

CVE-2023-53843 is a vulnerability in Linux, published on 9 Dec 2025. 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: reject negative ifindex

Recent changes in net-next (commit 759ab1edb56c ("net: store netdevs
in an xarray")) refactored the handling of pre-assigned ifindexes
and let syzbot surface a latent problem in ovs. ovs does not validate
ifindex, making it possible to create netdev ports with negative
ifindex values. It's easy to repro with YNL:

$ ./cli.py --spec netlink/specs/ovs_datapath.yaml \
         --do new \
	 --json '{"upcall-pid": 1, "name":"my-dp"}'
$ ./cli.py --spec netlink/specs/ovs_vport.yaml \
	 --do new \
	 --json '{"upcall-pid": "00000001", "name": "some-port0", "dp-ifindex":3,"ifindex":4294901760,"type":2}'

$ ip link show
-65536: some-port0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether 7a:48:21:ad:0b:fb brd ff:ff:ff:ff:ff:ff
...

Validate the inputs. Now the second command correctly returns:

$ ./cli.py --spec netlink/specs/ovs_vport.yaml \
	 --do new \
	 --json '{"upcall-pid": "00000001", "name": "some-port0", "dp-ifindex":3,"ifindex":4294901760,"type":2}'

lib.ynl.NlError: Netlink error: Numerical result out of range
nl_len = 108 (92) nl_flags = 0x300 nl_type = 2
	error: -34	extack: {'msg': 'integer out of range', 'unknown': [[type:4 len:36] b'\x0c\x00\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x0c\x00\x03\x00\xff\xff\xff\x7f\x00\x00\x00\x00\x08\x00\x01\x00\x08\x00\x00\x00'], 'bad-attr': '.ifindex'}

Accept 0 since it used to be silently ignored.

## Which versions are affected by CVE-2023-53843?


## How do I fix CVE-2023-53843?

Apply the vendor's patch.

## Is CVE-2023-53843 being exploited?

There is no known exploitation of CVE-2023-53843 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-53843 and fix it if it is affected.

What it is: CVE-2023-53843 is a vulnerability in Linux, published on 9 Dec 2025. 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-2023-53843 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-2023-53843/ (Markdown: https://insights.sbomify.com/CVE-2023-53843/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-53843
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-53843
- OSV: https://osv.dev/vulnerability/CVE-2023-53843

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-53843/
Summaries are generated and may contain mistakes; the official description above is the record.