# CVE-2026-41503: BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to 1.4.3, an out-of-bounds…

Source: https://junglewise.ai/threats/cve-2026-41503-bacnet-stack-is-a-bacnet-open-source-protocol-stack-c-library-for  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-24  
License: CC BY 4.0 with a link back

CVE-2026-41503 · Severity: high · CVSS 7.5 · Published 2026-04-24

BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to 1.4.3, an out-of-bounds read vulnerability in bacnet-stack's ReadPropertyMultiple service property decoder allows unauthenticated remote attackers to read past allocated buffer boundaries by sending an RPM request with a truncated property list. The vulnerability stems from rpm_decode_object_property() calling the deprecated decode_tag_number_and_value() function at src/bacnet/rpm.c:344, which accepts no buffer length parameter and reads blindly from whatever pointer it receives. A crafted BACnet/IP packet with a 1-byte property payload containing an extended tag marker (0xF9) causes the decoder to read 1 byte past the end of the buffer, leading to crashes on embedded BACnet devices. The vulnerability exists in src/bacnet/rpm.c and affects any deployment that enables the ReadPropertyMultiple confirmed service handler (enabled by default in the reference server). This vulnerability is fixed in 1.4.3.

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

## Quick answers

**Is CVE-2026-41503 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-41503 being exploited in the wild.

**How severe is CVE-2026-41503?** High severity, with a CVSS score of 7.5, published 24 April 2026.

**Which products and versions are affected?** Bacnetstack Bacnet Stack. The advisory does not name versions.

**Is there a fix for CVE-2026-41503?** 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.

**Am I affected by CVE-2026-41503?** Check whether you run Bacnetstack Bacnet Stack. 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.

## Affected products

- Bacnetstack Bacnet Stack

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