# CVE-2026-41503

> Vulnerability · severity: **HIGH** (CVSS 7.5).

## Description

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.

## Key facts

- **CVE ID:** CVE-2026-41503
- **Published:** 2026-04-24
- **CVSS severity:** HIGH
- **CVSS base score:** 7.5
- **CWE codes:** CWE-125

## Affected products

- `bacnetstack:bacnet_stack`

## Primary sources

- NIST NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-41503

## Citation

> AI Analytics. CVE-2026-41503. Retrieved 2026-07-08 from https://api.ai-analytics.org/cve/CVE-2026-41503. Derived from NIST NVD. Licensed CC0.

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