It wasn't smart of you to run an exploit you didn't understand on a box you didn't control. In this case, there was virtually no risk that you could have destabilized the machine. But for many of the last several years's Linux privilege escalation bugs, that isn't the case; they involve corrupting kernel memory and while the odds of them going seriously awry are remote, they aren't nonexistent.

To put this in perspective: assessing the security of app servers is my day job, and I would typically ask before running a privilege escalation exploit on a box I had gained access to.

Your boss overreacted, but unlike the rest of this thread, I don't think there are tea leaves to read. Had you done this on a prod server, your boss might have even been right.