CVE-2026-41503 is a high-severity out-of-bounds read vulnerability in BACnet Stack, an open-source protocol stack library for embedded systems. This vulnerability allows attackers to exploit the ReadPropertyMultiple service property decoder, leading to potential crashes of affected devices. The flaw exists in versions prior to 1.4.3, and its exploitation does not require authentication, making it particularly concerning for organizations utilizing BACnet Stack in their embedded systems.
The CVSS score for this vulnerability is 8.7, classified as high severity. The attack vector is network-based, with low complexity and no privileges required, meaning that attackers can exploit it without any prior access to the system. Risk to organizations includes significant availability impact, as the vulnerability may cause device crashes, leading to service interruptions.
Exploitation status indicates there are currently no known public exploits available, but the vulnerability remains critical due to its nature and the potential impact on operational environments. Organizations using BACnet Stack should prioritize remediation to safeguard their systems, especially considering that the vulnerability has been fixed in version 1.4.3.
Organizations should prioritize patching immediately to prevent unauthorized access and service disruptions. Timely updates and monitoring are crucial in mitigating the risks associated with this vulnerability.
Vulnerability Details
The vulnerability is characterized by an out-of-bounds read in bacnet-stack's ReadPropertyMultiple service property decoder. It arises from the rpm_decode_object_property() function calling the deprecated decode_tag_number_and_value() function, which lacks a buffer length parameter and reads indiscriminately from the provided pointer. As a result, a maliciously crafted BACnet/IP packet can cause the decoder to read beyond the allocated buffer, leading to device crashes.
The CVE was published on April 24, 2026, and is classified under CWE-125, indicating improper validation of buffer boundaries. Any deployment that enables the ReadPropertyMultiple confirmed service handler is affected, which is enabled by default in the reference server. The vulnerability is fixed in version 1.4.3.
Technical Analysis
The root cause of this vulnerability lies in the improper handling of input data within the BACnet protocol stack. The attack vector is network-based, allowing attackers to send specially crafted packets to exploit the vulnerability remotely. The complexity of the attack is low, requiring no special conditions, which makes it accessible to a wide range of attackers.
No user interaction is required for exploitation, and the confidentiality impact is rated as none. However, the integrity impact is also none, while the availability impact is high, as successful exploitation can lead to crashes of embedded BACnet devices.
Risk & Impact Analysis
Organizations utilizing BACnet Stack are at risk of significant operational disruptions due to this vulnerability. The ability for unauthenticated remote attackers to crash devices poses a critical threat, especially in environments where BACnet is used for controlling essential systems like HVAC or security.
With a CVSS score of 8.7, the urgency for remediation is high. Organizations should address this vulnerability in their priority patch cycle to mitigate risks effectively. The risk extends to all deployments that utilize the affected versions of BACnet Stack, highlighting the necessity for immediate action.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The vulnerability affects BACnet Stack versions prior to 1.4.3. Organizations utilizing these versions should update immediately to mitigate potential risks. If version information is not readily available, it is recommended to assume all versions prior to the vendor patch are affected.
Mitigation & Remediation
To remediate this vulnerability, organizations should upgrade to BACnet Stack version 1.4.3 or later, where the issue has been resolved. If immediate patching is not feasible, consider implementing network segmentation to limit exposure and monitor for unusual activity in BACnet communications. Additionally, ensure that proper logging and alerting mechanisms are in place to detect potential exploitation attempts.
For further guidance on securing embedded systems, organizations may look into our application security assessment services.
Detection Guidance
Organizations should monitor logs for any unusual BACnet/IP packet activity, specifically those containing extended tag markers that could indicate exploitation attempts. Additionally, review device behavior for crashes or unexpected reboots, which may suggest that the vulnerability is being exploited.
AppSecure Threat Intelligence Insight
The emergence of CVE-2026-41503 highlights the ongoing risks associated with network-exposed embedded systems and their vulnerabilities. This incident serves as a reminder for security teams to conduct regular vulnerability assessments and ensure that products are updated promptly. To enhance security posture, organizations should adopt a proactive approach to application security by implementing strategies such as continuous penetration testing and engaging in thorough red teaming exercises to identify and mitigate potential vulnerabilities before they can be exploited.
Furthermore, organizations should consider adopting best practices for penetration testing methodology to ensure comprehensive coverage of all potential attack vectors.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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