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Published: 5th March 2021

Version: 1.0.0

Severity: Medium

CVSS Score: 6.8 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N)


WSO2 IS as Key Manager : 5 .5.0 , 5.6.0 , 5.7.0 , 5.9.0 , 5.10.0
WSO2 Identity Server : 5.10.0  or earlier


One Time Password (OTP) usage in multi-factor authentication is vulnerable to brute force attacks.


When an OTP authenticator is configured as part of multi-factor authentication, it is possible to attempt brute forcing the OTP since those authenticators do not have a mechanism to prevent multiple failed attempts.


The probability of successful exploitation of this vulnerability is quite low because; (a) attacker needs to bypass the other steps in the authentication chain prior to this attack; (b) complexity of brute force attack depends on the number of digits of OTPs. If an attacker succeeds in brute forcing an OTP, it might be possible to gain access to the application by impersonating as a legitimate user. There could be an impact on the confidentiality, integrity and availability of the affected application based on the functionality provided to the user.


If you are using an affected product version, it is highly recommended to migrate to the latest released version to receive security fixes.

You may also apply the relevant fixes based on the changes from the public fix:,,

Note: If you are a WSO2 customer with Support Subscription, please use WSO2 Update Manager (WUM) updates in order to apply the fix.