Ilja van Sprundel of IOActive discovered several security issues in multiple components of the X.org graphics stack and the related libraries: Various integer overflows, sign handling errors in integer conversions, buffer overflows, memory corruption and missing input sanitising may lead to privilege escalation or denial of service.
For the oldstable distribution (squeeze), this problem will be fixed soon as version 1:1.1.0-2+squeeze1.
For the stable distribution (wheezy), this problem has been fixed in version 1:1.1.2-1+deb7u1.
For the unstable distribution (sid), this problem has been fixed in version 1:1.1.2-1+deb7u1.
We recommend that you upgrade your libxxf86vm packages.