[regularfry]

Sorry, would you mind clarifying? Any Ruby app? So a Sinatra app which happened to YAML.load would also be at risk?

[tptacek]

Yes, if attackers controlled the content of the YAML message.

[Turing_Machine]

In much the same way that letting attackers control the parameters to fork() would be a bad idea for a C program or letting attackers control the parameters to Runtime.exec() would be a bad idea for a Java program.

This is a Rails vulnerability, not a Ruby vulnerability.