CVE-2026-49341 in BACnet Stack
Summary
by MITRE • 11/13/2026
BACnet Stack is a BACnet open source protocol stack C library for embedded systems. Prior to version 1.5.1, there is a remotely reachable denial-of-service vulnerability in bacnet-stack affecting the default demo server built from the unmodified apps/server/main.c. This issue has been patched in version 1.5.1.
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Analysis
by VulDB Data Team • 11/13/2026
The BACnet Stack library serves as an open-source implementation of the Building Automation and Control Networks protocol, designed specifically for integration into embedded systems within smart building infrastructure. As a foundational C library, it facilitates communication between various devices such as HVAC controllers, lighting systems, and security sensors by handling the complex encoding and decoding required by the BACnet standard. The vulnerability identified in versions prior to 1.5.1 resides within the default demo server application, which is constructed from the unmodified source code located at apps/server/main.c. This specific component acts as a reference implementation for developers integrating BACnet capabilities into their hardware, but its inclusion of this flaw exposes critical infrastructure components when deployed without modification or additional security hardening measures.
The core technical flaw constitutes a remotely reachable denial-of-service vulnerability that allows an unauthenticated attacker to disrupt the availability of the affected service. By exploiting specific parsing errors or resource management issues within the BACnet protocol handling logic, an adversary can send malformed or specially crafted network packets that cause the server process to crash, hang, or enter an unrecoverable state. This type of flaw is characteristic of improper input validation and inadequate error handling during the processing of incoming protocol messages. The vulnerability aligns with CWE-20 Improper Input Validation and CWE-400 Uncontrolled Resource Consumption, as the system fails to properly validate the structure or length of received data before allocating resources or executing state transitions based on that data.
The operational impact of this vulnerability is significant within the context of building automation systems where reliability and continuous operation are paramount. A successful exploitation results in the complete unavailability of the BACnet service, effectively isolating the connected devices from the central management system. This disruption can lead to a loss of environmental control, such as heating or cooling failures, which may result in discomfort for occupants, potential damage to sensitive equipment due to temperature extremes, or even safety risks if fire suppression or alarm systems are dependent on the compromised node. Furthermore, because BACnet networks often rely on continuous polling and status updates, a single point of failure can cascade into broader network instability depending on the topology and redundancy mechanisms in place.
From an offensive security perspective, this vulnerability maps to MITRE ATT&CK technique T1499 Endpoint Denial of Service, specifically under sub-techniques involving application exhaustion or resource starvation. The remote nature of the exploit means that no physical access or prior authentication is required, allowing threat actors with network connectivity to the segment hosting the BACnet devices to execute this attack easily. This lowers the barrier for entry significantly compared to vulnerabilities requiring local execution or user interaction, making it a high-risk issue in environments where IoT and OT devices are connected directly to corporate networks without sufficient segmentation.
Mitigation strategies primarily involve upgrading the BACnet Stack library to version 1.5.1 or later, which includes patches addressing these specific parsing and resource management issues. For organizations unable to immediately update their software stack, network-level mitigations should be implemented to restrict access to the affected devices. This can include configuring firewalls or access control lists to limit traffic from untrusted networks to only necessary ports and protocols. Additionally, deploying intrusion detection systems tuned for BACnet anomalies can help identify attempts to exploit this vulnerability in real-time. It is also recommended that developers avoid using the default demo server configurations in production environments, opting instead for hardened implementations with strict input validation and resource limits applied manually if upgrading is not immediately feasible.