Description
The SSI printenv command in Apache Tomcat 9.0.0.M1 to 9.0.0.17, 8.5.0 to 8.5.39 and 7.0.0 to 7.0.93 echoes user provided data without escaping and is, therefore, vulnerable to XSS. SSI is disabled by default. The printenv command is intended for debugging and is unlikely to be present in a production website.
Mitigation
We recommend upgrading to a version of this component that is not vulnerable to this specific issue. If upgrading is not a viable option, this vulnerability can be mitigated by disabling the SSI functionality.