Medium · published October 8, 2026
The WSO2 Identity Server fails to enforce a default expiry time for SMS One-Time Passwords (OTPs) used in multi-factor authentication (MFA). This allows unused OTPs to remain valid indefinitely, presenting an opportunity for malicious actors to conduct brute force attacks by repeatedly guessing the OTP.
The absence of automatic expiration for OTPs grants attackers an unlimited timeframe to attempt guessing the correct code. A successful brute force attack can lead to an MFA bypass, resulting in the unauthorized takeover of a user's account and compromising the security and privacy of both the individual and the system.