A security vulnerability has been confirmed to exist in Apache Tomcat 4.0.x releases, which allows to use a specially crafted URL to return the unprocessed source of a JSP page, or, under special circumstances, a static resource which would otherwise have been protected by a security constraint, without the need for being properly authenticated. This is based on a variant of the exploit that was identified as CAN-2002-1148.
For the current stable distribution (woody) this problem has been fixed in version 4.0.3-3woody2.
The old stable distribution (potato) does not contain tomcat packages.
For the unstable distribution (sid) this problem does not exist in the current version 4.1.16-1.
We recommend that you upgrade your tomcat packages.