This is on the event of the last Ariane 5 launch, but the first Ariane 5 launch failed due to software.
The inertial reference system (SRI) was derived from Ariane 4. Since 5 was faster, a numeric conversion overflowed, which was not physically possible on 4. Since overflow was ‘impossible’, there was no explicit handling. Since the code was written in a ‘safe’ language (Ada), an ‘unsafe’ undefined result was impossible, so the module panicked. The SRI operation at that point was not actually required on the 5, but they had not wanted to make ‘unnecessary’ changes to disable it. Finally, the flight computer interpreted the SRI crash diagnostic data as flight data, and sent the rocket wildly off course.