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Vol. 1 · Ed. 2026
CyberGlossary
Entry № 253

Coverage-Guided Fuzzing

Reviewed byCybersecurity entrepreneur & security researcher

What is Coverage-Guided Fuzzing?

Coverage-Guided FuzzingA fuzzing technique that instruments the target to measure code coverage and evolves inputs that explore previously unseen paths, dramatically improving bug-finding efficiency.


Coverage-guided fuzzers instrument the target at compile time or via dynamic binary translation, then run candidate inputs while collecting edge or basic-block coverage. Inputs that exercise new coverage are kept and further mutated by an evolutionary algorithm, so the corpus drifts toward harder-to-reach code. This feedback loop, popularized by AFL and refined by AFL++, libFuzzer and Honggfuzz, is orders of magnitude more effective than blind random fuzzing on real software. It powers projects such as Google OSS-Fuzz, which has discovered tens of thousands of bugs in open-source code by running coverage-guided fuzzers continuously.

Examples

  1. 01

    Compiling a C parser with AFL++ instrumentation and using afl-fuzz to grow a coverage-driven corpus.

  2. 02

    libFuzzer using SanitizerCoverage to evolve inputs for a Rust crate.

Frequently asked questions

What is Coverage-Guided Fuzzing?

A fuzzing technique that instruments the target to measure code coverage and evolves inputs that explore previously unseen paths, dramatically improving bug-finding efficiency. It belongs to the Application Security category of cybersecurity.

What does Coverage-Guided Fuzzing mean?

A fuzzing technique that instruments the target to measure code coverage and evolves inputs that explore previously unseen paths, dramatically improving bug-finding efficiency.

How do you defend against Coverage-Guided Fuzzing?

Defences for Coverage-Guided Fuzzing typically combine technical controls and operational practices, as detailed in the full definition above.

What are other names for Coverage-Guided Fuzzing?

Common alternative names include: Greybox fuzzing, Feedback-driven fuzzing.

Related terms