# CVE-2025-66624: BACnet-stack MS/TP reply matcher OOB read

> An out-of-bounds read in the BACnet stack allows attackers to cause a denial of service via malformed packets.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 5 Dec 2025
- **Updated:** 8 Dec 2025
- **Also known as:** GHSA-8wgw-5h6x-qgqg

## What is CVE-2025-66624?

CVE-2025-66624 is a high-severity denial of service vulnerability in bacnet-stack, published on 5 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

BACnet Protocol Stack library provides a BACnet application layer, network layer and media access (MAC) layer communications services. Prior to 1.5.0.rc2, The npdu_is_expected_reply function in src/bacnet/npdu.c indexes request_pdu[offset+2/3/5] and reply_pdu[offset+1/2/4] without verifying that those APDU bytes exist. bacnet_npdu_decode() can return offset == 2 for a 2-byte NPDU, so tiny PDUs pass the version check and then get read out of bounds. On ASan/MPU/strict builds this is an immediate crash (DoS). On unprotected builds it is undefined behavior and can mis-route replies; RCE is unlikely because only reads occur, but DoS is reliable.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2025-66624?

It affects 1 product.


Products: Bacnetstack Bacnet Stack.

## How do I fix CVE-2025-66624?

No fix has been published for CVE-2025-66624 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-66624 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-66624 exists.

## Other vulnerabilities in bacnet-stack

- [CVE-2023-51773](https://insights.sbomify.com/CVE-2023-51773/): Memory corruption in n/a (critical 9.1)
- [CVE-2026-41475](https://insights.sbomify.com/CVE-2026-41475/): BACnet Stack: Out-of-Bounds Read in WritePropertyMultiple Decoder via Deprecated Tag Parser (high 8.7)
- [CVE-2026-41502](https://insights.sbomify.com/CVE-2026-41502/): BACnet Stack: Off-by-One Out-of-Bounds Read in ReadPropertyMultiple Object ID Decoder (high 8.7)
- [CVE-2026-41503](https://insights.sbomify.com/CVE-2026-41503/): BACnet Stack: Out-of-Bounds Read in ReadPropertyMultiple Property Decoder via Deprecated Tag Parser (high 8.7)
- [CVE-2026-26264](https://insights.sbomify.com/CVE-2026-26264/): BACnet Stack WriteProperty decoding length underflow leads to OOB read and crash (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-66624 and fix it if it is affected.

What it is: CVE-2025-66624 is a high-severity denial of service vulnerability in bacnet-stack, published on 5 Dec 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-2025-66624 exists.

Affected product: bacnet-stack. 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-2025-66624/ (Markdown: https://insights.sbomify.com/CVE-2025-66624/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-66624
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-66624
- OSV: https://osv.dev/vulnerability/CVE-2025-66624

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From sbomify Insights: https://insights.sbomify.com/CVE-2025-66624/
Summaries are generated and may contain mistakes; the official description above is the record.