CVE-2001-1152 in WEBsweeper
Summary
by MITRE
Baltimore Technologies WEBsweeper 4.02, when used to manage URL blacklists, allows remote attackers to bypass blacklist restrictions and connect to unauthorized web servers by modifying the requested URL, including (1) a // (double slash), (2) a /SUBDIR/.. where the desired file is in the parentdir, (3) a /./, or (4) URL-encoded characters.
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Analysis
by VulDB Data Team • 09/27/2025
This vulnerability exists in Baltimore Technologies WEBsweeper 4.02, a web content filtering solution designed to protect networks by blocking access to unauthorized websites through URL blacklists. The flaw represents a significant security bypass issue that undermines the fundamental purpose of the filtering system. The vulnerability stems from inadequate input validation and URL parsing mechanisms within the software's blacklist enforcement logic, allowing malicious actors to manipulate requested URLs to circumvent restrictions.
The technical exploitation occurs through specific URL manipulation techniques that exploit path traversal and normalization weaknesses in the web filtering engine. Attackers can bypass restrictions by appending double slashes // which may cause the system to interpret the URL differently, using directory traversal sequences like /SUBDIR/.. to navigate to parent directories where restricted content might be accessible, employing forward slash dot slash /./ sequences that are often normalized by web servers but not properly handled by the filtering software, or utilizing URL-encoded characters to obfuscate their attempts. These techniques leverage the way the software processes and normalizes URLs during the filtering decision-making process.
The operational impact of this vulnerability is substantial as it completely defeats the purpose of web content filtering for organizations relying on WEBsweeper 4.02. Organizations may experience unauthorized access to restricted websites including malicious domains, corporate data exfiltration, or access to inappropriate content, depending on the nature of the blacklisted sites. This vulnerability particularly affects environments where web filtering is critical for compliance, security policy enforcement, or protecting against malicious web traffic, potentially exposing sensitive networks to attacks that could otherwise be prevented by the filtering system.
The vulnerability aligns with CWE-22 Path Traversal and CWE-120 Buffer Overflow in its exploitation patterns, representing a classic case of insufficient input sanitization and improper URL handling. From an adversarial perspective, this vulnerability maps to ATT&CK technique T1071.004 Application Layer Protocol HTTP, where attackers leverage protocol weaknesses to bypass network controls, and T1068 Local Privilege Escalation through network access bypass. Organizations should immediately update to a patched version of WEBsweeper, implement additional network-level filtering controls, and conduct thorough audits of their existing blacklists to identify potential bypasses. The vulnerability underscores the critical importance of proper URL normalization and input validation in security appliances, particularly those handling network access control decisions where the consequences of bypasses can be severe.