Open redirect vulnerability in the Forms Authentication feature in the ASP.NET subsystem in Microsoft .NET Framework 2.0 SP2, 3.5 SP1, 3.5.1, and 4.0 allows remote attackers to redirect users to arbitrary web sites and conduct phishing attacks via a crafted return URL, aka "Insecure Redirect in .NET Form Authentication Vulnerability."

Open redirect vulnerability in the Forms Authentication feature in the ASP.NET subsystem in Microsoft .NET Framework 2.0 SP2, 3.5 SP1, 3.5.1, and 4.0 allows remote attackers to redirect users to arbitrary web sites and conduct phishing attacks via a crafted return URL, aka "Insecure Redirect in .NET Form Authentication Vulnerability."

ASP.NET provided by Microsoft contains an open redirect vulnerability due to an issue in the login component. ASP.NET provided by Microsoft contains an open redirect vulnerability due to an issue in the login component. Therefore a web application that implements ASP.NET may be vulnerable. Tomoki Sanaki of NTT Communications Corporation Security Operation Center reported this vulnerability to IPA. JPCERT/CC coordinated with the developer under Information Security Early Warning Partnership.