# CVE-2026-46677: BACnet Stack out-of-bounds read in AtomicReadFile-ACK

Source: https://junglewise.ai/threats/cve-2026-46677-bacnet-stack-is-a-bacnet-open-source-protocol-stack-c-library-for  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-12. Updated: 2026-11-12  
License: CC BY 4.0 with a link back

CVE-2026-46677 · Severity: medium · CVSS 6.5 · Published 2026-11-12

BACnet Stack is a C library implementing the BACnet protocol, widely used in building automation and HVAC systems. A remote attacker can send a crafted network message that causes the library to read beyond allocated memory, potentially exposing sensitive data or crashing devices that process BACnet file transfer requests.

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

## Quick answers

**Is CVE-2026-46677 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-46677 being exploited in the wild.

**How severe is CVE-2026-46677?** Medium severity, with a CVSS score of 6.5, published 12 November 2026.

**Which products and versions are affected?** BACnet Stack prior to 1.4.4 and 1.5.1.

**Is there a fix for CVE-2026-46677?** Yes: fixed in 1.4.4, 1.5.1. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-46677 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-46677?** Check whether you run 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.

## How to fix

- Fixed in 1.4.4, 1.5.1

## Technical details

A client-side stack out-of-bounds read occurs in the AtomicReadFile-ACK decoder when the remote returnedRecordCount exceeds the fixed BACNET_READ_FILE_RECORD_COUNT array capacity. The decode path preserves the oversized count without truncation, and downstream code iterates over this count while accessing the undersized fileData[] array without bounds checking. An unauthenticated remote attacker can trigger this by sending an AtomicReadFile ACK message with RecordCount greater than the local array size.

## Affected products

- BACnet Stack BACnet Stack prior to 1.4.4 and 1.5.1

## Timeline

- 2026-11-12: disclosed: CVE-2026-46677 published
- 2026-05-13: patched: Fix merged in PR #1344

## References

- [https://github.com/bacnet-stack/bacnet-stack/pull/1344](https://github.com/bacnet-stack/bacnet-stack/pull/1344)
- [https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-rv5h-cxwq-q3mh](https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-rv5h-cxwq-q3mh)

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