CVE-2003-0105 in ServerMask
Summary
by MITRE
ServerMask 2.2 and earlier does not obfuscate (1) ETag, (2) HTTP Status Message, or (3) Allow HTTP responses, which could tell remote attackers that the web server is an IIS server.
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Analysis
by VulDB Data Team • 06/08/2024
This vulnerability resides in ServerMask 2.2 and earlier versions of the web server masking software, which fails to properly obfuscate critical HTTP response headers that reveal underlying server identification information. The flaw specifically affects three key HTTP response elements: ETag headers, HTTP Status Messages, and Allow headers, all of which can inadvertently disclose that the web server is running Microsoft Internet Information Services. The vulnerability represents a classic information disclosure issue that falls under the CWE-200 category of "Information Exposure" and aligns with ATT&CK technique T1592.004 for "Resource Discovery" through server identification enumeration. When these headers remain unobfuscated, they create a fingerprint that attackers can use to identify the specific server software and version, which is crucial information for planning targeted attacks against known vulnerabilities in IIS.
The technical implementation of this vulnerability stems from ServerMask's incomplete header sanitization process, where it successfully obscures some HTTP headers but leaves critical identification elements untouched. ETag headers often contain server-specific identifiers that can reveal the underlying platform, while HTTP Status Messages may include version information or server-specific language that indicates IIS as the backend. The Allow header, which specifies supported HTTP methods, can also contain server-specific patterns that help identify the web server type. This incomplete obfuscation creates a false sense of security where administrators believe their server masking is effective, but attackers can still gather intelligence through careful analysis of these remaining unmasked elements. The vulnerability directly impacts the principle of defense in depth by creating information leakage channels that bypass the intended security controls.
The operational impact of this vulnerability extends beyond simple information disclosure, as it significantly weakens the overall security posture of web applications running on IIS servers. Attackers can use the revealed server identification to tailor their exploitation strategies, focusing on known vulnerabilities specific to IIS versions rather than employing generic attack vectors. This intelligence gathering capability enables more sophisticated and effective attacks, including exploitation of version-specific vulnerabilities, privilege escalation opportunities, and targeted social engineering campaigns. The vulnerability also undermines the effectiveness of security through obscurity, a fundamental security principle where the goal is to make systems harder to attack by concealing their characteristics. From an ATT&CK perspective, this vulnerability supports techniques such as T1082 for system information discovery and T1592 for adversary behavior in identifying target systems, making it particularly dangerous in environments where server identification is crucial for maintaining operational security.
Organizations should implement comprehensive mitigation strategies that include upgrading to ServerMask versions that properly obfuscate all HTTP headers, implementing additional web application firewalls that can further mask server identification information, and conducting regular security audits to verify that all headers are properly sanitized. The mitigation approach should align with security frameworks like NIST SP 800-53 controls for information system monitoring and security assessment. Organizations should also consider implementing automated tools that can scan for such information disclosure vulnerabilities and establish continuous monitoring processes to detect when server identification information leaks through other channels. Regular security training for administrators should emphasize that complete header sanitization is required and that partial obfuscation can still provide attackers with sufficient information to compromise systems. The vulnerability demonstrates the importance of thorough security testing and validation of security controls before deployment, particularly for tools designed to obscure system information.