OpenBSD 3.8, 3.9, and possibly earlier versions allows context-dependent attackers to cause a denial of service (kernel panic) by allocating more semaphores than the default.
https://exchange.xforce.ibmcloud.com/vulnerabilities/28617
http://www.securityfocus.com/bid/19713
http://www.openbsd.org/errata38.html#sem
http://www.openbsd.org/errata.html#sem