CVE-2026-41502

Description

BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to 1.4.3, an off-by-one out-of-bounds read vulnerability in bacnet-stack's ReadPropertyMultiple service decoder allows unauthenticated remote attackers to read one byte past an allocated buffer boundary by sending a crafted RPM request with a truncated object identifier. The vulnerability is in rpm_decode_object_id(), which checks apdu_len < 5 but then accesses all 6 byte positions (indices 0-5) — consuming 1 byte for the context tag, 4 bytes for the object ID, then reading apdu[5] for the opening tag check. A 5-byte input passes the length check but causes a 1-byte OOB read, 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.

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CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0025

Probability of exploitation

0.48%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-125 Out-of-bounds Read

CWE-193 CWE-193

Affected Products

Vendor	Product	Versions
bacnetstack	bacnet_stack	1.4.0 — 1.4.3
bacnetstack	bacnet_stack	All
bacnetstack	bacnet_stack	All
bacnetstack	bacnet_stack	All

References

Advisories & Patches

https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-7545-3fpx-4xw3 https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-7545-3fpx-4xw3

Exploits

https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-7545-3fpx-4xw3 https://github.com/bacnet-stack/bacnet-stack/security/advisories/GHSA-7545-3fpx-4xw3

Frequently Asked Questions

What is CVE-2026-41502? +

BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to 1.4.3, an off-by-one out-of-bounds read vulnerability in bacnet-stack's ReadPropertyMultiple service decoder allows unauthenticated remote attackers to read one byte past an allocated buffer boundary by sending a crafted RPM request with a truncated object identifier. The vulnerability is in rpm_decode_object_id(), which checks apdu_len < 5 but then accesses all 6 byte positions (indices 0-5) — consuming 1 byte for the context tag, 4 bytes for the object ID, then reading apdu[5] for the opening tag check. A 5-byte input passes the length check but causes a 1-byte OOB read, 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. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-41502? +

CVE-2026-41502 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0025, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-41502? +

CVE-2026-41502 affects products from bacnetstack, specifically: bacnet_stack. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-41502? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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