CVE-2006-6104 in Mono
Summary
by MITRE
The System.Web class in the XSP for ASP.NET server 1.1 through 2.0 in Mono does not properly verify local pathnames, which allows remote attackers to (1) read source code by appending a space (%20) to a URI, and (2) read credentials via a request for Web.Config%20.
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Analysis
by VulDB Data Team • 06/15/2025
The vulnerability identified as CVE-2006-6104 affects the System.Web class implementation within Mono's XSP (XmlHttpRequest Server Protocol) for ASP.NET versions 1.1 through 2.0. This represents a critical path traversal and information disclosure weakness that fundamentally undermines the security boundaries of web applications running on the Mono platform. The flaw exists in how the server processes local pathnames, creating a pathway for remote attackers to bypass normal access controls and gain unauthorized access to sensitive application resources.
The technical mechanism behind this vulnerability stems from inadequate input validation within the pathname handling logic of the XSP server. When attackers append a space character represented as %20 to a URI, the server fails to properly sanitize or validate the request path, allowing it to traverse the file system and access files that should remain protected. This occurs because the server does not properly canonicalize or resolve the requested path, enabling attackers to exploit directory traversal patterns that should be rejected by proper path validation mechanisms. The vulnerability specifically targets the handling of Web.Config files and source code files, which contain sensitive information including database connection strings, authentication credentials, and application configuration details that are typically protected from direct web access.
The operational impact of this vulnerability is severe and multifaceted, encompassing both information disclosure and potential credential theft. Attackers can leverage this weakness to extract source code files containing business logic, implementation details, and potentially sensitive algorithms that could be used for further exploitation. More critically, the ability to access Web.Config files provides unauthorized access to application credentials, connection strings, and other sensitive configuration data that could enable attackers to escalate their privileges within the application environment. This vulnerability essentially allows attackers to bypass authentication mechanisms and directly access resources that should only be available to authorized users or system processes, creating a significant risk for applications handling sensitive data.
This vulnerability maps directly to CWE-22 (Improper Limitation of a Pathname to a Restricted Directory) and CWE-23 (Relative Path Traversal), both of which are fundamental path traversal weaknesses that have been consistently exploited across various web platforms. From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1213.002 (Data from Information Repositories) and T1566.001 (Phishing with Social Engineering) as attackers can use the information disclosure to gather intelligence for more sophisticated attacks. The vulnerability also intersects with ATT&CK technique T1078.004 (Valid Accounts: Cloud Accounts) when credentials from Web.Config files are used to access cloud resources or additional systems. Organizations should implement immediate mitigations including updating to patched versions of Mono, implementing proper input validation at the application level, and configuring web servers to reject requests containing suspicious path characters or sequences.
The remediation strategy for this vulnerability requires both immediate and long-term approaches to ensure comprehensive protection. Organizations must upgrade to patched versions of Mono that address the pathname validation issues in the XSP server implementation, as the vulnerability exists in core server functionality that cannot be effectively mitigated through configuration changes alone. Additionally, implementing proper input validation at the application level, including canonicalization of all file paths and rejection of requests containing suspicious characters, provides an additional layer of defense. Network-level protections such as web application firewalls should be configured to detect and block requests containing path traversal sequences, while proper file system permissions and access controls should be enforced to limit what files can be accessed even if the vulnerability is exploited. Regular security assessments and penetration testing should verify that the patched environment properly handles all potential traversal scenarios and that no similar weaknesses exist in other components of the web application stack.