JunOS is based on FreeBSD, which doesn't have a fix yet. Not sure about the different variants of Cisco IOS. You wouldn't run untrusted code on a router though,

JunOS is based on FreeBSD, which doesn't have a fix yet. Not sure about the different variants of Cisco IOS. You wouldn't run untrusted code on a router though, so spectre would not be a concern. In fact, it's probably better not to patch for it given the performance degradation.