CVE-2011-4110 on Ubuntu 12.04 LTS (precise) - medium.
Description:
The user_update function in security/keys/user_defined.c in the Linux kernel 2.6 allows local users to cause a denial of service (NULL pointer dereference and kernel oops) via vectors related to a user-defined key and "updating a negative key into a fully instantiated key." A flaw was found in how the Linux kernel handles user-defined key types. An unprivileged local user could exploit this to crash the system.