The case of the 9 bit AES key

Security firm V12 reports that several PDF tools generate AES-256 file keys from tiny, guessable state. In MuPDF before 1.28.5, only nine bits of the timestamp seed affect the key, so 512 candidates cover every case and a Python search takes about 11 ms. Foxit Reader hashes a timestamp with zero-filled bytes, and a Rust search covers every second since 1970 in under five seconds. OpenPDF and iText are also affected. MuPDF is fixed; the findings are the authors' own and unverified independently.