Mutation Fuzzing

Mutation fuzzers start with a corpus of valid inputs — sample images, network packets, documents — and apply small random changes (bit flips, byte substitutions, block deletions, splices) to generate new candidates. Unlike generation-based fuzzers, they do not need a grammar of the input format, which makes them quick to deploy on any parser or protocol. When combined with coverage feedback, mutation fuzzers like AFL++ and libFuzzer can quickly evolve inputs that explore deep code paths and trigger memory-safety bugs. They are widely used to harden codecs, file parsers, kernel drivers and cryptographic libraries during the SSDLC.