Google rewrote giflib in Rust using Gemini

Google described a pilot to rewrite the C library giflib (~3000 lines) into an ABI-compatible Rust version using Gemini: bit-for-bit regression on 30+ million real GIFs and 200+ million iterations of differential fuzzing showed no discrepancies, and systems that had already migrated were immune to the later-disclosed CVE-2026-26740.

Compiled by Sergey KostenchukPublished 2026-08-31Updated 2026-09-18

2026-08-31 Coding Google

💻 Google rewrote giflib in Rust using Gemini

Google Bug Hunters engineers rewrote ~3000 lines of GIF decoder from C to Rust — an ABI-compatible drop-in replacement. Regression on 30+ million real GIFs gave bit-for-bit match; differential fuzzing (200+ million iterations) — no discrepancies. When CVE-2026-26740 was disclosed in giflib 5.2.2, Google's migrated systems were immune.

🌍 About 70% of vulnerabilities in C/C++ are memory issues. Google showed a pipeline: LLM rewriting, unsafe code review, differential fuzzing, deployment with rollback. CVE-2026-26740 proved: migration closes not-yet-disclosed zero-days as a class.

👤 The C/Rust FFI boundary remains an unsafe zone, trust in generated code is earned through validation. The differential testing methodology can be reused in your own migrations.

Source 1: https://bughunters.google.com/blog/scaling-memory-safety Source 2: https://nvd.nist.gov/vuln/detail/CVE-2026-26740

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