CVE-2001-0507 in IIS
Summary
by MITRE
IIS 5.0 uses relative paths to find system files that will run in-process, which allows local users to gain privileges via a Trojan horse file, aka the "System file listing privilege elevation" vulnerability.
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Analysis
by VulDB Data Team • 10/06/2025
The vulnerability described in CVE-2001-0507 represents a critical privilege escalation flaw in Microsoft Internet Information Services version 5.0 that stems from improper handling of relative paths during system file resolution. This vulnerability specifically affects the way IIS 5.0 processes file paths when executing in-process components, creating an exploitable condition that allows local attackers to elevate their privileges through the strategic placement of malicious files within the system hierarchy. The flaw exploits the inherent trust model of the web server's file resolution mechanism, where relative paths are interpreted without sufficient validation of the actual file location.
The technical implementation of this vulnerability occurs when IIS 5.0 resolves relative paths to system files that are intended to run in-process within the web server environment. When a local user places a malicious Trojan horse file in a location that matches a relative path used by the system, the web server will execute this malicious file with the privileges of the IIS process rather than the user who placed the file. This creates a privilege escalation scenario where the local attacker can effectively execute code with elevated permissions, potentially gaining system-level access to the host machine. The vulnerability is particularly dangerous because it leverages the trust relationship between the web server and its file resolution mechanisms, bypassing normal access controls that would otherwise prevent such privilege elevation.
From an operational perspective, this vulnerability presents significant risk to organizations running IIS 5.0 servers, particularly those with multiple local user accounts or systems where users might have the ability to place files in directories accessible to the web server. The attack vector is straightforward and requires only local access to the system, making it particularly dangerous in environments where users have shell access or file system permissions that allow them to place files in strategic locations. The impact extends beyond simple privilege escalation as the compromised IIS process could potentially provide access to sensitive system resources, databases, or other applications running on the same host. This vulnerability directly relates to CWE-22, which addresses improper limitation of a pathname to a restricted directory, and falls under the ATT&CK technique T1068 for local privilege escalation through system binary manipulation.
Mitigation strategies for this vulnerability should focus on implementing proper path validation and access controls within the IIS configuration. Organizations should immediately apply the security patches released by Microsoft for this vulnerability, as the fix involves modifying the way IIS 5.0 resolves relative paths to prevent execution of unauthorized files. System administrators should also implement strict file system permissions, ensuring that the IIS process runs with minimal required privileges and that the web server directory structure properly isolates executable components from user-accessible directories. Additionally, implementing the principle of least privilege for IIS processes, disabling unnecessary features, and conducting regular security audits of web server configurations can help prevent exploitation of this and similar path traversal vulnerabilities. The vulnerability underscores the importance of proper input validation and path resolution mechanisms in web server implementations, particularly when dealing with in-process execution contexts that can potentially elevate privileges.