CVE-2012-3382 in Mono
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the ProcessRequest function in mcs/class/System.Web/System.Web/HttpForbiddenHandler.cs in Mono 2.10.8 and earlier allows remote attackers to inject arbitrary web script or HTML via a file with a crafted name and a forbidden extension, which is not properly handled in an error message.
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Analysis
by VulDB Data Team • 12/31/2024
The CVE-2012-3382 vulnerability represents a critical cross-site scripting flaw within the Mono web framework implementation that affects versions 2.10.8 and earlier. This vulnerability specifically targets the ProcessRequest function located in the mcs/class/System.Web/System.Web/HttpForbiddenHandler.cs file, which serves as the core component responsible for handling forbidden HTTP requests. The flaw arises from inadequate sanitization of user-supplied input when processing files with crafted names containing forbidden extensions, creating a pathway for malicious actors to execute arbitrary web scripts or HTML code within the context of vulnerable applications.
The technical exploitation of this vulnerability occurs when a remote attacker submits a file request with a specially crafted filename that includes a forbidden extension. When the Mono framework processes this request, it generates an error message that fails to properly escape or sanitize the malicious input before rendering it to the user's browser. This improper handling creates an XSS vector where attacker-controlled content can be executed within the victim's browser context, potentially leading to session hijacking, credential theft, or redirection to malicious sites. The vulnerability operates at the application layer and requires no authentication to exploit, making it particularly dangerous in web environments where file uploads or name validation are common operations.
The operational impact of this vulnerability extends beyond simple script execution, as it can be leveraged to bypass security controls and compromise user sessions within applications running on affected Mono versions. Attackers can craft malicious filenames that, when processed by the HttpForbiddenHandler, will inject scripts into error messages displayed to users. This allows for persistent XSS attacks that can affect multiple users visiting the vulnerable application, potentially leading to widespread compromise of user data and application integrity. The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws in web applications, and represents a classic example of insufficient output escaping in error handling scenarios. The attack surface is particularly broad given that many web applications rely on Mono's HTTP handling components for file validation and access control mechanisms.
Mitigation strategies for CVE-2012-3382 require immediate patching of affected Mono installations to versions 2.10.9 or later where the vulnerability has been addressed through proper input sanitization and output escaping in error message generation. Organizations should implement comprehensive input validation mechanisms that reject or sanitize filenames containing potentially malicious extensions before they reach the HttpForbiddenHandler component. Additionally, developers should ensure that all error messages generated by web applications properly escape user-supplied content using appropriate encoding mechanisms such as HTML entity encoding or JavaScript context escaping. Security monitoring should include detection of unusual file upload patterns and malformed requests that might indicate exploitation attempts. The vulnerability demonstrates the critical importance of proper error handling and input validation in web frameworks, aligning with ATT&CK technique T1211 which covers the exploitation of input validation weaknesses in web applications. Organizations should also consider implementing web application firewalls and content security policies to provide additional layers of protection against such XSS vectors.