The Apollo 11 Guidance Computer Had a Four-Byte Bug. It Hid for 57 Years.

The most reviewed code ever written had a four-byte bug. No bug detector found it. No static analyzer warned about it. No end-to-end test case triggered it. 57 years. Four lines. The Apollo Guidance Computer source code has been public since 2003. Thousands of developers have read it. Academics published papers on its reliability. Emulators run it instruction by instruction. The transcription was verified byte-for-byte against the original core rope dumps. A team at JUXT just found a resource lock leak in the gyro control code that could have silently killed the guidance platform's ability to realign. Four bytes. Two missing instructions. The Lock That Nobody Released Here's what happened. The AGC manages the spacecraft's Inertial Measurement Unit through a shared lock called LGYRO. When the computer needs to torque the gyroscopes to correct drift or perform a star alignment, it grabs the lock, does the work across three axes, and releases it when done. → Normal path: lock acquired, to