This indicates an attack attempt to exploit a Directory Traversal vulnerability in Nostromo web server.
The vulnerability is due to insufficient sanitizing of user supplied inputs in the application when handling a crafted HTTP. A remote attacker may be able to exploit this to access local file on the systems, leading to possible remote code execution.
Nostromo version 1.9.6 and prior
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.