# CVE-2026-38570: BACnet Stack out-of-bounds read in bacnet_tag_number_decode

Source: https://junglewise.ai/threats/cve-2026-38570-bacnet-stack-out-of-bounds-read-in-bacnet-tag-number-decode  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-04. Updated: 2026-06-04  
License: CC BY 4.0 with a link back

CVE-2026-38570 · Severity: info · CVSS 7.5 · Published 2026-06-04

The BACnet Stack library, which provides communication services for building automation and control networks, contains a vulnerability in its data decoding component. An attacker can send a specially crafted network message to trigger a crash in the software. This results in a denial-of-service condition, potentially disrupting the monitoring and control of building systems like HVAC, lighting, and access control.

Technologies: [BACnet Stack Project BACnet Stack](https://junglewise.ai/threats/technologies/bacnet-stack). Vendors: [BACnet Stack Project](https://junglewise.ai/threats/vendors/bacnet-stack-project).

## Quick answers

**Is CVE-2026-38570 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-38570 being exploited in the wild.

**How severe is CVE-2026-38570?** Informational severity, with a CVSS score of 7.5, published 4 June 2026.

**Which products and versions are affected?** BACnet Stack Project BACnet Stack 1.3.1.

**Is there a fix for CVE-2026-38570?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-38570 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-38570?** Check whether you run BACnet Stack Project BACnet Stack at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

An out-of-bounds (OOB) read vulnerability exists in BACnet Stack 1.3.1 within the bacnet_tag_number_decode function. The root cause is a failure in bacapp_decode_application_data() to validate an oversized extended application length against the actual remaining bytes in the APDU. This malformed length is passed through bacapp_decode_data() to host_n_port_decode(), which subsequently triggers an invalid memory read in bacnet_tag_number_decode(). A remote, unauthenticated attacker can exploit this by sending a malformed UCOV (Unconfirmed Change of Value) or property-value payload, leading to a segmentation fault and denial of service.

## Affected products

- BACnet Stack Project BACnet Stack 1.3.1

## Timeline

- 2026-06-04: disclosed: Vulnerability reported via GitHub Issues and published to NVD.

## References

- [https://github.com/bacnet-stack/bacnet-stack](https://github.com/bacnet-stack/bacnet-stack)
- [https://github.com/bacnet-stack/bacnet-stack/issues/1270](https://github.com/bacnet-stack/bacnet-stack/issues/1270)

## Related threats

- [BACnet Stack stack-buffer-overflow in Loop object property read](https://junglewise.ai/threats/cve-2026-47710-bacnet-stack-is-a-bacnet-open-source-protocol-stack-c-library-for)
- [BACnet Stack out-of-bounds read in AtomicWriteFile](https://junglewise.ai/threats/cve-2026-46674-bacnet-stack-is-a-bacnet-open-source-protocol-stack-c-library-for)