[kabdib]

Fuzzing was used in Thomas J Ryan's The Adolescence of P-1, circa 1977 (in an attack against some IBM mainframe's supervisor).

(TAoP1 is a much-overlooked example of . . . well, I wouldn't call it cyberpunk, but definitely counter-culture computing. In the IBM world, I think that means you refuse to wear a tie. It's technically dated -- think modems-and-megabytes -- but still kind of fun).

[bitwize]

Vernor Vinge did write True Names, which is often considered a foundational cyberpunk text (even predating Gibson).