Race condition in Linux 2.6, when threads are sharing memory mapping via CLONE_VM (such as linuxthreads and vfork), might allow local users to cause a denial of service (deadlock) by triggering a core dump while waiting for a thread that has just performed an exec.
Ubuntu Security Notice USN-199-1 - Multiple vulnerabilities exist in both linux-source-2.6.10 and linux-source-2.6.8. These include race conditions and denial of service flaws.