David Tomaschik

**Name of the Vulnerable Software and Affected Versions** Software House iStar Ultra versions through 6.5.2.20569 **Description** A door-unlocking issue was discovered when the Software House iStar Ultra is used with the IP-ACM Ethernet Door Module. The communications between the IP-ACM and the iStar Ultra use a fixed AES key and IV for encryption in CBC mode, which allows for replay attacks of entire messages. Additionally, the lack of message authentication beyond the fixed AES key enables message forgery. **Recommendations** For versions through 6.5.2.20569, consider disabling the IP-ACM Ethernet Door Module until a patch is available to prevent potential replay attacks and message forgery. Restrict access to the device to minimize the risk of exploitation. At the moment, there is no information about a newer version that contains a fix for this issue.