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

> Attackers can bypass firewall filters to inject or observe multicast traffic when management IP filtering is disabled on Hirschmann HiLCOS devices.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 3 Apr 2026
- **Updated:** 25 May 2026
- **Also known as:** GHSA-w392-grj8-mrrf

## What is CVE-2017-20233?

CVE-2017-20233 is a medium-severity vulnerability in Belden Hirschmann HiLCOS BAT867, published on 3 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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.

Weakness: CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2017-20233?


## How do I fix CVE-2017-20233?

No fix has been published for CVE-2017-20233 yet. Limit exposure of the affected software until one is available.

## Is CVE-2017-20233 being exploited?

There is no known exploitation of CVE-2017-20233 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2017-20233 and fix it if it is affected.

What it is: CVE-2017-20233 is a medium-severity vulnerability in Belden Hirschmann HiLCOS BAT867, published on 3 Apr 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-2017-20233 in the wild and no public exploit code.

Affected product: Belden Hirschmann HiLCOS BAT867. 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-2017-20233/ (Markdown: https://insights.sbomify.com/CVE-2017-20233/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2017-20233
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-20233
- OSV: https://osv.dev/vulnerability/CVE-2017-20233

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From sbomify Insights: https://insights.sbomify.com/CVE-2017-20233/
Summaries are generated and may contain mistakes; the official description above is the record.