Some Linksys E-Series Routers are vulnerable to an unauthenticated OS command injection. This vulnerability was used from the so called "TheMoon" worm. There are many Linksys systems that might be vulnerable including E4200, E3200, E3000, E2500,...
Linksys E-Series TheMoon Remote Command Injection
E-Series Routers are vulnerable to an unauthenticated OS command injection