Joe Orton discovered a cross site scripting problem in mod_ssl, an Apache module that adds Strong cryptography (i.e. HTTPS support) to the webserver. The module will return the server name unescaped in the response to an HTTP request on an SSL port.
Like the other recent Apache XSS bugs, this only affects servers using a combination of "UseCanonicalName off" (default in the Debian package of Apache) and wildcard DNS. This is very unlikely to happen, though. Apache 2.0/mod_ssl is not vulnerable since it already escapes this HTML.
With this setting turned on, whenever Apache needs to construct a self-referencing URL (a URL that refers back to the server the response is coming from) it will use ServerName and Port to form a "canonical" name. With this setting off, Apache will use the hostname:port that the client supplied, when possible. This also affects SERVER_NAME and SERVER_PORT in CGI scripts.
This problem has been fixed in version 2.8.9-2.1 for the current stable distribution (woody), in version 2.4.10-1.3.9-1potato4 for the old stable distribution (potato) and version 2.8.9-2.3 for the unstable distribution (sid).
We recommend that you upgrade your libapache-mod-ssl package.