syracom AG Secure Login (2FA) for Atlassian Jira, Confluence, and Bitbucket 3.4.0.x contains an authentication bypass vulnerability. An attacker with valid credentials for a user account can bypass the two-factor authentication flow by sending HTTP requests with a crafted User-Agent header containing specific strings such as AtlassianMobileApp or JIRA. When such a User-Agent is present, the plugin does not enforce the configured 2FA checks for protected web resources. Successful exploitation allows the attacker to access the affected Atlassian application as the compromised user without completing 2FA. If the compromised account has administrative privileges, the attacker can access administrative functionality and may disable the 2FA plugin or make arbitrary administrative changes. The issue is fixed in version 3.5.0.0.