We caught a capacity overflow bug in Bark before it ever hit a user—thanks to the fuzz testing @luca0x46 has been running around the clock. A malformed VTXO could have requested an arbitrary vec size during deserialization, triggering a panic. Now it's patched.
Bark's client-server architecture means the server has to gracefully handle anything thrown at it—malformed VTXOs, malicious client requests, unexpected edge cases. Fuzzing helps make sure the server stays up and keeps serving rounds no matter what comes in.
The vec allocation bug is a good example of something easy to miss in review—stable Rust doesn't yet support try_with_capacity, so the bounds check has to be done manually. Our first fuzz target was a straightforward deserialize/serialize pass, and it surfaced the issue immediately.
The fuzzer runs 24/7 now, with minimized corpora pushed to our bark-qa repo alongside test vectors used throughout Bark's development. More targets coming—serialization/deserialization expansions first, then method-level fuzz targets.
Full writeup:
https://blog.second.tech/fuzzing-bark-for-server-reliability/
