The (1) CHAP and (2) MS-CHAP-V2 authentication capabilities in the PPP Access Concentrator (PPPAC) function in Internet Initiative Japan SEIL/B1 firmware 1.00 through 2.52 use the same challenge for each authentication attempt, which allows remote attackers to bypass authentication via a replay attack.

The (1) CHAP and (2) MS-CHAP-V2 authentication capabilities in the PPP Access Concentrator (PPPAC) function in Internet Initiative Japan SEIL/B1 firmware 1.00 through 2.52 use the same challenge for each authentication attempt, which allows remote attackers to bypass authentication via a replay attack.

SEIL/B1 contains an issue in the implementation of the PPP Access Concentrator (PPPAC) function, which may allow replay attacks to be performed during the authentication process. The PPP Access Concentrator (PPPAC) function within SEIL/B1 contains an issue in the CHAP and MS-CHAP-V2 authentication processes, the same challenge value is repeatedly used for each authentication attempt.