CVE-2001-0506 in IIS
Summary
by MITRE
Buffer overflow in ssinc.dll in IIS 5.0 and 4.0 allows local users to gain system privileges via a Server-Side Includes (SSI) directive for a long filename, which triggers the overflow when the directory name is added, aka the "SSI privilege elevation" vulnerability.
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Analysis
by VulDB Data Team • 02/15/2025
The CVE-2001-0506 vulnerability represents a critical buffer overflow flaw in the Server-Side Includes (SSI) functionality of Microsoft Internet Information Services versions 4.0 and 5.0. This vulnerability specifically affects the ssinc.dll component which handles SSI directives, creating a pathway for local attackers to escalate their privileges to system level access. The flaw manifests when processing SSI directives that reference long filenames, where the buffer overflow occurs during the concatenation of directory names, effectively allowing attackers to manipulate memory structures within the IIS process.
This vulnerability operates through a classic buffer overflow mechanism where insufficient input validation occurs when handling filename strings in SSI processing. The ssinc.dll library fails to properly bounds-check the length of filenames passed through SSI directives, particularly when these filenames are combined with directory path components. When an attacker crafts a malicious SSI directive with an excessively long filename, the concatenated string exceeds the allocated buffer space, causing memory corruption that can be exploited to execute arbitrary code with elevated privileges. The vulnerability is particularly dangerous because it requires only local access to the system, making it accessible to users who already have basic system credentials.
The operational impact of CVE-2001-0506 extends beyond simple privilege escalation as it provides attackers with complete system control capabilities. Once exploited, the vulnerability allows adversaries to execute commands with SYSTEM privileges, potentially leading to full system compromise, data exfiltration, and persistence mechanisms. The attack vector is relatively straightforward since it only requires local access and the ability to create or modify SSI-enabled web content, making it particularly concerning for environments where local user accounts might be compromised. This vulnerability aligns with CWE-121, which describes unsafe array indexing in buffer overflow scenarios, and demonstrates the classic attack pattern documented in the ATT&CK framework under privilege escalation techniques.
Mitigation strategies for CVE-2001-0506 focus primarily on immediate patching of affected IIS versions, as Microsoft released security updates specifically addressing this vulnerability. Organizations should implement strict input validation measures for SSI directives and consider disabling SSI functionality if not essential for operations. Network segmentation and privilege separation can help limit the impact if exploitation occurs, while monitoring for unusual SSI directive usage patterns can aid in early detection. The vulnerability highlights the importance of proper bounds checking in legacy applications and demonstrates why maintaining up-to-date security patches remains critical for preventing exploitation of known vulnerabilities in web server environments.