Technical Tip: Unable to log in to FortiGate GUI after upgrading to v7.6.4 with post-login banner

[lkumar]

Description	This article describes an issue where an administrator fails to log in to the GUI using either local or remote user accounts after upgrading to firmware version 7.6.4, when the post-login banner is enabled.
Scope	FortiGate v7.6.4.
Solution	After upgrading to version 7.6.4, administrators are unable to log in to the GUI using either local or remote user accounts. After entering valid credentials, the GUI displays an authentication failure message. This issue is triggered only when the post-login banner is enabled. Logging in through the CLI continues to work normally, even when the post-login banner is enabled. Note: The issue occurs only while accessing the device via the management interface. Successful authentication can be verified using the following debugs: diagnose debug application httpsd -1 diagnose debug application http_authd -1 diagnose debug enable This issue has been resolved in: v7.6.5 (available to download from the Fortinet Support portal). v8.0.0 (scheduled to be released in March 2026). These timelines for firmware release are estimated and may be subject to change. Workaround: Disable the post-login banner using the following CLI commands: Verify current setting: get system global | grep post-login Disable banner: config system global     set post-login-banner disable end Confirm the change: get system global | grep post-login