Microsoft IIS 4.0/5.0 Malformed Filename Request Vulnerability

Bugtraq ID:	1193
Class:	Access Validation Error
CVE:
Remote:	Yes
Local:	Yes
Published:	May 11 2000 12:00AM
Updated:	May 11 2000 12:00AM
Credit:	Discovered by Cerberus Security Team <[email protected]> and publicized in a Microsoft Security Bulletin (MS00-031).
Vulnerable:	Microsoft IIS 5.0 - Microsoft Windows 2000 Advanced Server SP2 - Microsoft Windows 2000 Advanced Server SP2 - Microsoft Windows 2000 Advanced Server SP1 - Microsoft Windows 2000 Advanced Server SP1 + Microsoft Windows 2000 Advanced Server + Microsoft Windows 2000 Advanced Server - Microsoft Windows 2000 Datacenter Server SP2 - Microsoft Windows 2000 Datacenter Server SP2 - Microsoft Windows 2000 Datacenter Server SP1 - Microsoft Windows 2000 Datacenter Server SP1 - Microsoft Windows 2000 Professional SP2 - Microsoft Windows 2000 Professional SP2 - Microsoft Windows 2000 Professional SP1 - Microsoft Windows 2000 Professional SP1 + Microsoft Windows 2000 Professional + Microsoft Windows 2000 Professional - Microsoft Windows 2000 Server SP2 - Microsoft Windows 2000 Server SP2 - Microsoft Windows 2000 Server SP1 - Microsoft Windows 2000 Server SP1 + Microsoft Windows 2000 Server + Microsoft Windows 2000 Server Microsoft IIS 4.0 alpha - Microsoft Windows NT 4.0 alpha - Microsoft Windows NT 4.0 alpha Microsoft IIS 4.0 + Cisco Building Broadband Service Manager (BBSM) 5.0 + Cisco Building Broadband Service Manager (BBSM) 5.0 + Cisco Call Manager 3.0 + Cisco Call Manager 3.0 + Cisco Call Manager 2.0 + Cisco Call Manager 2.0 + Cisco Call Manager 1.0 + Cisco Call Manager 1.0 + Cisco ICS 7750 + Cisco ICS 7750 + Cisco IP/VC 3540 Video Rate Matching Module + Cisco IP/VC 3540 Video Rate Matching Module + Cisco Unity Server 2.4 + Cisco Unity Server 2.4 + Cisco Unity Server 2.3 + Cisco Unity Server 2.3 + Cisco Unity Server 2.2 + Cisco Unity Server 2.2 + Cisco Unity Server 2.0 + Cisco Unity Server 2.0 + Cisco uOne 4.0 + Cisco uOne 4.0 + Cisco uOne 3.0 + Cisco uOne 3.0 + Cisco uOne 2.0 + Cisco uOne 2.0 + Cisco uOne 1.0 + Cisco uOne 1.0 + Hancom Hancom Office 2007 0 + Hancom Hancom Office 2007 0 + Microsoft BackOffice 4.5 + Microsoft BackOffice 4.5 + Microsoft Windows NT 4.0 Option Pack + Microsoft Windows NT 4.0 Option Pack
Not Vulnerable:

Microsoft IIS 4.0/5.0 Malformed Filename Request Vulnerability

Requesting a known filename with the extension replaced with .htr preceeded by approximately 230 "%20" (which is an escaped character that represents a space) from Microsoft IIS 4.0/5.0 will cause the server to retrieve the file and its contents. This is due to the .htr file extension being mapped to ISM.DLL ISAPI application which redirects .htr file requests to ISM.DLL. ISM.DLL removes the extraneous "%20" and replaces .htr with the proper filename extension and reveals the source of the file. This vulnerability is similar to a more recently discovered variant, BugTraq ID 1488.

This action can only be performed if a .htr request has not been previously made or if ISM.DLL is loaded into memory for the first time. If an .htr request has already been made, a restart of the web server is necessary in order to perform another.

Microsoft IIS 4.0/5.0 Malformed Filename Request Vulnerability

http://target/filename%20(repeated approx 230 times).htr

Microsoft IIS 4.0/5.0 Malformed Filename Request Vulnerability

References:

• Frequently Asked Questions: Microsoft Security Bulletin (MS00-031) (Microsoft)
  
• Microsoft IIS 4.0/5.0 Source Fragment Disclosure Vulnerability (SecurityFocus)
  
• Q260069: Malformed HTR Request Returns Source Code for ASP Scripting Files (Microsoft)
  
• Q260838: IIS Stops Servicing HTR Requests (Microsoft)