AES-256 Encryption in Multiple PDF Editors Found Trivially Breakable

Security team V12sec disclosed that AES-256 encryption in multiple PDF implementations, including MuPDF, generates file encryption keys with only about 9 bits of randomness, allowing attackers to decrypt documents without the password—some weak enough to break by hand.

2026-10-29 ~ 2026-10-29 · 2 related posts

• Multiple PDF tools' AES-256 encryption trivially broken—MuPDF key has only 9 bits of entropy — jedisct1 · 2026-10-29
• PDF editors' AES-256 encryption so broken some keys can be cracked by hand — matthew_d_green · 2026-10-29