Poppler 0.42.0 through 26.10.0 contains a stack-based buffer overflow in Decrypt::revision6Hash() that allows attackers controlling the password to overwrite stack memory when opening AESV3/R6 encrypted PDFs. Attackers can supply a password longer than 127 bytes through applications using the libpoppler, libpoppler-glib or C++ API to overflow the K1 and E buffers, crashing the process or corrupting memory.