I believe the bug in su was found earlier; I remember that if you type a password and follow it with the encrypted password, you would get in. Looking at the code, you'd need to make sure that the encrypted password of the password you just typed in would need to be at position 105 (100+"root:")

Casper

From: Alan Coopersmith <alan.coopersmith () oracle com> Sent: 05 January 2026 18:27 To: oss-security () lists openwall com Subject: [External] : [oss-security] Buffer overflow in /bin/su from UNIX v4

Late last year, a tape was found containing the only known copy of Bell Labs Research Unix Version 4 from 1973 - the version in which UNIX was rewritten from assembly into the then-new C programming language. Since then a number of folks have been running the recovered software in PDP-11 simulators.

https://urldefense.com/v3/https://sigma-star.at/blog/2025/12/unix-v4-buffer-overflow/;!!ACWV5N9M2RV99hQ!Px94aM2iBzLwDRhX4zhSX89cVDosduXv7mNqmv7HMgwJHi4FhtNHHhlzrhKONdsG8YQvXzRqmsruAgbbjwwY8jw3A$ examines the source code for su.c and shows that the buffer for password input is a simple 100 character array, but the loop to read password input has no boundary checks and will happily keep writing long past the end of the buffer.

Doug McIlroy from the original Bell Labs Unix team points out that "Overflowable buffers were common in those days." and that there are likely more to be found in the UNIX v4 source code, in the thread at https://urldefense.com/v3/https://www.tuhs.org/pipermail/tuhs/2026-January/032966.html;!!ACWV5N9M2RV99hQ!Px94aM2iBzLwDRhX4zhSX89cVDosduXv7mNqmv7HMgwJHi4FhtNHHhlzrhKONdsG8YQvXzRqmsruAgbbjwKopG4mw$

-- -Alan Coopersmith- alan.coopersmith () oracle com Oracle Solaris Engineering - https://blogs.oracle.com/solaris