Pedro Ribeiro from Agile Information Security found a possible remote code execution on Horde3, a web application framework. Unsanitized variables are passed to the unserialize() PHP function. A remote attacker could specially-craft one of those variables allowing her to load and execute code.
For the oldstable distribution (squeeze), this problem has been fixed in version 3.3.8+debian0-3.
In the testing (jessie) and unstable (sid) distributions, Horde is distributed in the php-horde-util package. This problem has been fixed in version 2.3.0-1.
We recommend that you upgrade your horde3 packages.