eLabFTW is an open source electronic lab notebook for research labs. A vulnerability has been found starting in version 4.6.0 and prior to version 5.1.0 that allows an attacker to bypass eLabFTW's built-in multifactor authentication mechanism. An attacker who can authenticate locally (by knowing or guessing the password of a user) can thus log in regardless of MFA requirements. This does not affect MFA that are performed by single sign-on services. Users are advised to upgrade to at least version 5.1.9 to receive a fix.