CVE-2001-0658 in ISA Server
Summary
by MITRE
Cross-site scripting (CSS) vulnerability in Microsoft Internet Security and Acceleration (ISA) Server 2000 allows remote attackers to cause other clients to execute certain script or read cookies via malicious script in an invalid URL that is not properly quoted in an error message.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 10/05/2025
The vulnerability identified as CVE-2001-0658 represents a critical cross-site scripting flaw within Microsoft Internet Security and Acceleration ISA Server 2000, classified under CWE-79 as improper neutralization of input during web page generation. This vulnerability exists in the server's handling of malformed URL requests and specifically manifests when the server generates error messages that fail to properly quote or escape script content, creating an environment where malicious actors can inject arbitrary code into client-side web browsers.
The technical exploitation of this vulnerability occurs through the manipulation of URL parameters that the ISA Server processes and subsequently displays in error messages without adequate sanitization. When a malformed URL is submitted to the server, the ISA Server generates an error response that contains unescaped script code within the URL parameter, which is then executed by the victim's browser when the error page is rendered. This improper handling of user input directly violates security principles established in the OWASP Top Ten and represents a classic example of a server-side injection vulnerability that can be leveraged for session hijacking, data theft, or client-side compromise.
The operational impact of CVE-2001-0658 extends beyond simple script execution as it enables attackers to perform cookie theft and session manipulation attacks against authenticated users of the ISA Server. This vulnerability can be exploited through various attack vectors including phishing campaigns, social engineering, or direct web-based exploitation where malicious URLs are crafted to exploit the unescaped error messages. The attack surface is particularly concerning given that ISA Server 2000 was commonly deployed as a corporate firewall and web proxy solution, making it a prime target for attackers seeking to compromise enterprise networks and access sensitive internal resources.
Mitigation strategies for this vulnerability must address both the immediate exposure and underlying architectural issues that enable the attack. Microsoft released security patches for ISA Server 2000 that properly escape and sanitize error messages before displaying them to clients, ensuring that any user-supplied input is neutralized before being rendered in web contexts. Organizations should implement comprehensive input validation at all network boundaries, deploy web application firewalls to detect and block malicious script injection attempts, and conduct regular security assessments of their proxy and firewall configurations. The vulnerability also highlights the importance of following the principle of least privilege in network security implementations and demonstrates how legacy systems can present significant security risks when not properly maintained with security updates. This vulnerability aligns with ATT&CK technique T1566 which covers social engineering tactics, particularly through phishing, as attackers can craft malicious URLs that exploit this flaw to establish persistent access to target networks.