Software Engineering Institute

ProCheckup Ltd has reported a vulnerability in RSA Security ACE/Agent for Windows, ACE/Agent for Windows NT, and ACE/Agent for Windows 2000. The Windows versions of ACE/Agent can be used to protect resources on Microsoft Internet Information Server (IIS) web servers. Protected resources include directories, files, and executable programs. Requests for protected resources are passed from the web server to the ACE/Agent, which is implemented in the file sdiis.dll. The ACE/Agent authenticates the request against an RSA Security ACE/Server using RSA Security's SecurID technology. While processing a crafted HTTP request containing URL encoded characters, ACE/Agent does not properly decode the characters and therefore does not recognize that the request is for a protected resource. As a result, ACE/Agent does not perform authentication and allows the web server to return the requested resource.

RSA Security addressed this issue in July 2001. The following ACE/Agents are not affected:

• RSA ACE/Agent 4.4.3 (or later) for Windows NT
• RSA ACE/Agent 1.1.2 (or later) for Windows 2000
• RSA ACE/Agent 5.0 for Windows

An attacker may bypass authentication and view protected files and execute programs on the web server.

This vulnerability is fixed in the versions of ACE/Agents specified in the Vendor Statement. RSA Security recommends that customers install the latest releases, which are available through RSA Security's SecurCare Online and through RSA Security's public web site. RSA Security informed customers of this vulnerability in a Security Bulletin dated July 24, 2001.

IIIb. Workarounds
It may be possible to use an application layer filter to detect and block malicious requests.