CVE-2009-4535 in Mongoose
Summary
by MITRE
Mongoose 2.8.0 and earlier allows remote attackers to obtain the source code for a web page by appending a / (slash) character to the URI.
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Analysis
by VulDB Data Team • 07/07/2025
The vulnerability identified as CVE-2009-4535 affects the Mongoose web server version 2.8.0 and earlier, presenting a significant information disclosure risk that can be exploited by remote attackers. This flaw manifests when a malicious actor appends a forward slash character to a URI, enabling them to access the source code of web pages that would otherwise be protected or restricted. The issue represents a critical misconfiguration in the web server's directory traversal and access control mechanisms, fundamentally undermining the security boundaries that should protect sensitive web content from unauthorized access.
The technical root cause of this vulnerability lies in the improper handling of URI requests within the Mongoose web server implementation. When a request is made to a directory path without a trailing slash, the server fails to properly validate or sanitize the incoming URI before processing the request. This allows attackers to manipulate the request structure by simply appending a slash character, which causes the server to return the source code of the web page instead of executing it properly. The vulnerability essentially bypasses the intended access controls and file serving mechanisms, exposing the underlying source code to remote adversaries. This behavior aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal attacks. The flaw demonstrates a fundamental weakness in input validation and request processing that enables attackers to access resources they should not be permitted to view.
The operational impact of this vulnerability extends beyond simple information disclosure, as the exposed source code can contain sensitive elements such as database connection strings, API keys, configuration parameters, and application logic that could be leveraged for further attacks. Attackers can exploit this vulnerability to gain insights into the application architecture, identify potential security weaknesses in the codebase, and potentially discover additional vulnerabilities that may exist within the system. This information disclosure can lead to more sophisticated attacks including credential theft, privilege escalation, and other advanced persistent threats that exploit the knowledge gained from the exposed source code. The vulnerability can be exploited through simple web browser requests or automated tools, making it particularly dangerous as it requires minimal technical expertise to execute successfully. According to ATT&CK framework, this vulnerability maps to T1566.001, which covers Phishing with Malicious Attachment, as the exposed source code could contain malicious payloads or reveal information that enables more targeted phishing attacks. The accessibility of this vulnerability through standard web browsing operations also aligns with T1071.001, which covers Application Layer Protocol: Web Protocols, indicating how attackers can leverage common web protocols to achieve their objectives.
Mitigation strategies for CVE-2009-4535 should focus on immediate patching of the Mongoose web server to version 2.8.1 or later, which contains the necessary fixes to address the improper URI handling behavior. Organizations should also implement proper input validation and sanitization measures at the web server level to prevent malformed URI requests from being processed in ways that could expose source code. Network-level controls including web application firewalls and access control lists can provide additional protection by filtering suspicious URI patterns and preventing unauthorized access attempts. Security monitoring should be enhanced to detect unusual access patterns that might indicate exploitation attempts, particularly requests with trailing slashes to directory paths. Regular security assessments and source code reviews should be conducted to identify similar vulnerabilities in other web applications and services, ensuring comprehensive protection against information disclosure attacks. The remediation process should also include updating security configurations to enforce proper access controls and implementing defense-in-depth strategies that prevent attackers from gaining unauthorized access to sensitive web resources.