ysoserial vs libformatstr.py: 2026 Comparison
ysoserial is a free penetration testing tool. libformatstr.py is a free penetration testing tool. Compare features, ratings, integrations, and community reviews side by side to find the best penetration testing fit for your security stack.
CST VerdictBased on our analysis of available product data, here is our conclusion:
Penetration testers and red teamers validating Java deserialization vulnerabilities need ysoserial for its breadth of gadget chains; with 8,501 GitHub stars and active community contributions, it remains the de facto standard for generating CVE-2015-6420 and related payloads across legacy and modern Java frameworks. The tool's strength lies in its ability to craft working exploits against unsafe ObjectInputStream implementations without requiring live target interaction during payload generation. Skip this if your scope is limited to .NET or Python applications, or if you need a guided UI; ysoserial is command-line native and demands familiarity with Java serialization mechanics.
Penetration testers who regularly target legacy C applications will move faster with libformatstr.py because its automated parameter detection eliminates the manual trial-and-error that makes format string exploitation tedious. The library's 347 GitHub stars and active use in professional engagements confirm it handles real payloads, not toy examples. Skip this if your work centers on modern memory-safe languages or you need something with a GUI; libformatstr.py is Python-first and assumes comfort reading code.
