signed applications with large jnlp file cannot be launched

When trying to launch signed applications with a JNLP file that is larger than 1024 bytes, javaws freezes while displaying the splash screen. The freeze occurs while trying to validate JNLP-INF/APPLICATION.JNLP from the signed jar.

This bug has already been fixed upstream:
http://icedtea.classpath.org/bugzilla/show_bug.cgi?id=898
http://icedtea.classpath.org/hg/release/icedtea-web-1.2/rev/dde230f3536a

Users cannot circumvent this issue and I'd prefer not having to advise them to manually install Oracle Java instead, especially with all the security implications resulting from doing so.

Description: Ubuntu 12.04.1 LTS
Release: 12.0

icedtea-netx:
Installed: 1.2-2ubuntu1.2