This indicates an attack attempt against a directory-traversal vulnerability in OSSIM os-sim.
The vulnerability is caused by an error when the vulnerable software handles a specially crafted URL. It allows a remote attacker to view arbitrary local files and directories within the context of the webserver.
OSSIM os-sim 2.2 and prior version
Information disclosure: Malicious users may be able to bypass certain security restrictions and compromise a vulnerable system.
Upgrade to later versions.