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.
https://exchange.xforce.ibmcloud.com/vulnerabilities/91316
http://www.nongnu.org/oath-toolkit/NEWS.html
http://seclists.org/oss-sec/2014/q1/296
http://lists.nongnu.org/archive/html/oath-toolkit-help/2013-12/msg00003.html
http://lists.nongnu.org/archive/html/oath-toolkit-help/2013-12/msg00002.html
http://lists.nongnu.org/archive/html/oath-toolkit-help/2013-12/msg00000.html