Say nothing to Houston: decades old bug found in Apollo guidance system code

9 April 2026

JUXT, a software consultancy based in the United Kingdom, report discovering a bug in the code of the Apollo Guidance Computer, nearly fifty-four years after the last Apollo Moon flight:

The Apollo Guidance Computer (AGC) is one of the most scrutinised codebases in history. Thousands of developers have read it. Academics have published papers on its reliability. Emulators run it instruction by instruction. We found a bug in it that had been missed for fifty-seven years: a resource lock in the gyro control code that leaks on an error path, silently disabling the guidance platform’s ability to realign.

The guidance systems were installed in both the command module, and lunar module (the vessel that landed on the Moon), of the Apollo craft.

Thankfully, the bug didn’t manifest itself during the Apollo missions. There’s enough happening during a flight to the Moon without wanting to worry about patches for software bugs.

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science, space exploration, technology