Yamcs up to 5.9.3 Authentication AuthHandler.java redirect_uri cross site scripting

Summaryinfo

A vulnerability described as problematic has been identified in Yamcs up to 5.9.3. Affected by this issue is some unknown functionality of the file yamcs-core/src/main/java/org/yamcs/http/auth/AuthHandler.java of the component Authentication. The manipulation of the argument redirect_uri results in cross site scripting. This vulnerability is known as CVE-2026-55549. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability was found in Yamcs up to 5.9.3. It has been classified as problematic. Affected is an unknown code block of the file yamcs-core/src/main/java/org/yamcs/http/auth/AuthHandler.java of the component Authentication. The manipulation of the argument redirect_uri with an unknown input leads to a cross site scripting vulnerability. CWE is classifying the issue as CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. This is going to have an impact on integrity. CVE summarizes:

Yamcs is a mission control framework. Prior to 5.9.4, Yamcs reflects an attacker-controlled redirect_uri parameter from GET /auth/authorize into yamcs-core/src/main/resources/auth/templates/authorize.html without adequate HTML escaping by yamcs-core/src/main/java/org/yamcs/http/auth/AuthHandler.java and yamcs-core/src/main/java/org/yamcs/http/HandlerContext.java. A crafted authorization URL can execute JavaScript when opened by a Yamcs user. The script can access browser-held authentication material and transmit it to an attacker, enabling account compromise. This issue is fixed in version 5.9.4.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-55549 since 06/17/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Successful exploitation requires user interaction by the victim. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1059.007 by the MITRE ATT&CK project.

Upgrading to version 5.9.4 eliminates this vulnerability.

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Productinfo

Name

• Yamcs

Version

• 5.9.0
• 5.9.1
• 5.9.2
• 5.9.3

Website

• Product: https://github.com/yamcs/yamcs/

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