CVE-2026-55549

Name of the Vulnerable Software and Affected Versions Yamcs versions prior to 5.9.4

Description A Reflected Cross-Site Scripting (XSS) issue exists where the application reflects the redirect uri parameter from the 'GET /auth/authorize' endpoint into the authorize.html template without adequate HTML escaping. This occurs within the AuthHandler.java and HandlerContext.java files. An attacker can use a crafted authorization URL to execute arbitrary JavaScript in a user's browser, allowing them to access and exfiltrate browser-held authentication material, such as session tokens and refresh tokens, leading to full account compromise.

Recommendations Update to version 5.9.4.