The use of single-factor authentication can lead to unnecessary risk of compromise when compared with the benefits of a dual-factor authentication scheme.
Extended description
While the use of multiple authentication schemes is simply piling on more complexity on top of authentication, it is inestimably valuable to have such measures of redundancy. The use of weak, reused, and common passwords is rampant on the internet. Without the added protection of multiple authentication schemes, a single mistake can result in the compromise of an account. For this reason, if multiple schemes are possible and also easy to use, they should be implemented and required.
Best practices to prevent this CWE
Phase: Architecture and Design
Use multiple independent authentication schemes, which ensures that -- if one of the methods is compromised -- the system itself is still likely safe from compromise.