What port was this sent to, and what webserver are you running (if it was sent to a webserver)?
This reminds me of the string to strigger the really bad apache vulnerabilities that lead to being able to read from the whole filesystem (path traversal), or get a shell on your system (remote code execution). It's likelu that bots are spray and praying attempts across the internet. As long as you're up to date, you should be good.