Unearthing Hidden Bugs: Harnessing Fuzzing With Dynamic Patching in FlakJack

This thesis presents a study on the fuzzing of Linux binaries to find occluded bugs. Fuzzing is a widely-used technique for identifying software bugs. Despite their effectiveness, state-of-the-art fuzzers suffer from limitations in efficiency and effectiveness. Fuzzers based on random mutations are fast but struggle to generate high-quality inputs. In contrast, fuzzers based on symbolic execution produce quality inputs but lack execution speed. This paper proposes FlakJack, a novel hybrid fuzzer that patches the binary on the go to detect occluded bugs guarded by surface bugs. To dynamically overcome the challenge of patching binaries, the paper introduces multiple patching strategies based on the type of bug detected. The performance of FlakJack was evaluated on ten widely-used real-world binaries and one chaff dataset binary. The results indicate that many bugs found recently were already present in previous versions but were occluded by surface bugs. FlakJack’s approach improved the bug-finding ability by patching surface bugs that usually guard occluded bugs, significantly reducing patching cycles. Despite its unbalanced approach compared to other coverage-guided fuzzers, FlakJack is fast, lightweight, and robust. False- Positives can be filtered out quickly, and the approach is practical in other parts of the target. The paper shows that the FlakJack approach can significantly improve fuzzing performance without relying on complex strategies.