Apache httpd 1.3.37, 2.0.59, and 2.2.4 with the Prefork MPM module, allows local users to cause a denial of service by modifying the worker_score and process_score arrays to reference an arbitrary process ID, which is sent a SIGUSR1 signal from the master process, aka "SIGUSR1 killer."
Exploitability
AV:LAC:MAu:NImpact
C:NI:NA:C4.7/AV:L/AC:M/Au:N/C:N/I:N/A:C