# CVE-2020-36872: BACnet Test Server 1.01 Malformed BVLC Length DoS

> Remote attackers can crash the BACnet Test Server by sending malformed BVLC length values, causing a denial of service.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 26 Nov 2025
- **Updated:** 28 Jul 2026
- **Also known as:** GHSA-3v4j-cjvq-5p59

## What is CVE-2020-36872?

CVE-2020-36872 is a high-severity denial of service vulnerability in BACnet Test Server, published on 26 Nov 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

BACnet Test Server versions up to and including 1.01 contains a remote denial of service vulnerability in its BACnet/IP BVLC packet handling. The server fails to properly validate the BVLC Length field in incoming UDP BVLC frames on the default BACnet port (47808/udp). A remote unauthenticated attacker can send a malformed BVLC Length value to trigger an access violation and crash the application, resulting in a denial of service.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2020-36872?


## How do I fix CVE-2020-36872?

No fix has been published for CVE-2020-36872 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-36872 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2020-36872 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-36872 and fix it if it is affected.

What it is: CVE-2020-36872 is a high-severity denial of service vulnerability in BACnet Test Server, published on 26 Nov 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2020-36872 exists.

Affected product: BACnet Test Server. 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-2020-36872/ (Markdown: https://insights.sbomify.com/CVE-2020-36872/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-36872
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-36872
- OSV: https://osv.dev/vulnerability/CVE-2020-36872

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From sbomify Insights: https://insights.sbomify.com/CVE-2020-36872/
Summaries are generated and may contain mistakes; the official description above is the record.