They weren't based on the same novel -- but the novels "Fail Safe" and "Red Alert" were similar enough, and the release dates of "Fail Safe" and "Dr. Strangelove" were so close that Peter George and Stanley Kubrick sued the author and production of Fail Safe over copyright. In the eventual settlement, Columbia Pictures bought and distributed Fail Safe.

[I'm basing this on a reading of Wikipedia - https://en.wikipedia.org/wiki/Fail_Safe_(1964_film)#Lawsuit ]