Skip to content
NewA calmer, faster ZeroHour
Researchinfo

Project Zero: BigSleep beat Fuzzilli on V8 bugs, overlap partial

Original title: Fuzzers vs. AI: Comparing Fuzzilli and BigSleep on JavaScript Engines

Google Project Zeroby Samuel Groß ()14 min read1
Read at projectzero.google
AI summary · x-ai/grok-4.7Summaries by Vani AI

In six months BigSleep reported 45 V8 vulnerabilities to Fuzzilli's 37, and experiments put theoretical overlap near 60%.

Google Project Zero compared Fuzzilli, a generative JavaScript fuzzer, with BigSleep, an LLM-based bug finder, on Chrome's V8 engine. From April through September 2026, BigSleep found more vulnerabilities than Fuzzilli, 45 versus 37, with 25% overlap in the specific bugs reported. Dedicated experiments on vulnerabilities reported since 2023 estimated overlap at roughly 60%. The team says many bugs were found by only one method and recommends vendors run both fuzzing and agentic analysis.

Unconfirmed: Reported-bug overlap is 25%, while a separate experiment estimates about 60%; the excerpt does not give final actionable totals.

Key facts
  • Unfiltered reports totaled 316 for Fuzzilli and 441 for BigSleep.
  • Issues typed as vulnerabilities were 178 for Fuzzilli and 95 for BigSleep.
  • Fuzzilli runs continuously; BigSleep reviews new commits about once a day.
  • Both systems file reports through ClusterFuzz into Chrome's issue tracker.
  • The excerpt ends before final counts of actionable, fixed vulnerabilities.
Security assessment · AI, from the article
What to do
  1. 1.Run both fuzzing and agentic code analysis to maximize vulnerabilities found before users are affected.
Analyze this story with Vani AIImpact, who is affected and what defenders should do, in a new chat
Tags
v8fuzzingjavascriptproject-zerobigsleepfuzzilli
Vendors
Google
Products
ChromeV8FuzzilliBigSleepClusterFuzz
Organizations
Project Zero

From the original article

14 min read at projectzero.google

Summary Project Zero compared two automated tools used by Google to find vulnerabilities in Chrome’s JavaScript engine, V8, on a regular basis. Fuzzilli is a generative JavaScript engine fuzzer and BigSleep is an LLM-based bug finding system. In the past six months, BigSleep found more vulnerabilities than Fuzzilli (45 versus 37) with a 25% overlap in the specific bugs reported.

Google Project Zero

By Samuel Groß · projectzero.google

Read the full article at Google Project Zero

A short excerpt; the article and its images belong to the publisher. Summary, key facts and assessment above are AI-written from the article and can be wrong.