Deserialization of untrusted data

usersfile.c in liboath in OATH Toolkit before 2.4.1 does not properly handle lines containing an invalid one-time-password (OTP) type and a user name in /etc/users.oath, which causes the wrong line to be updated when invalidating an OTP and allows context-dependent attackers to conduct replay attacks, as demonstrated by a commented out line when using libpam-oath.