CVE-2004-2604 in PHProxy
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in index.php in PHProxy allows remote attackers to inject arbitrary web script or HTML via the error parameter.
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Analysis
by VulDB Data Team • 05/29/2019
The vulnerability identified as CVE-2004-2604 represents a classic cross-site scripting flaw within the PHProxy web proxy application's index.php script. This security weakness specifically targets the error parameter handling mechanism, creating an avenue for malicious actors to execute arbitrary web scripts or HTML code within the context of other users' browsers. The vulnerability operates at the application layer and demonstrates a fundamental failure in input validation and output sanitization practices that were prevalent in web applications during the early 2000s era.
The technical implementation of this XSS vulnerability stems from the improper handling of user-supplied input through the error parameter in the PHProxy application. When the application processes this parameter without adequate sanitization or encoding, it directly incorporates the malicious payload into the web response sent to the victim's browser. This creates a persistent vector where attackers can craft specially formatted error messages containing malicious script code that executes in the victim's browser context. The vulnerability falls under CWE-79 which specifically addresses improper neutralization of input during web page generation, making it a direct manifestation of weak input validation mechanisms.
The operational impact of this vulnerability extends beyond simple script execution as it provides attackers with the capability to perform session hijacking, deface web applications, steal sensitive user information, or redirect users to malicious websites. In the context of a web proxy application like PHProxy, this vulnerability becomes particularly dangerous because it can be exploited to manipulate the proxy's functionality and potentially gain unauthorized access to web resources that the proxy is designed to mediate. Attackers could leverage this weakness to inject malicious code that would execute whenever legitimate users interact with the proxy interface, creating a persistent threat vector.
The exploitation of CVE-2004-2604 aligns with several tactics described in the ATT&CK framework under the T1566 category for initial access through social engineering, where the malicious payload could be delivered via crafted error messages or through phishing campaigns that direct users to exploit the vulnerability. Organizations using PHProxy or similar web proxy applications would be particularly vulnerable to this type of attack, as the proxy's intended function of masking user identity and accessing restricted content becomes compromised when attackers can inject malicious code into the proxy's interface. The vulnerability demonstrates the critical importance of implementing proper input validation and output encoding mechanisms that are consistent with modern web security best practices.
Mitigation strategies for this vulnerability should focus on implementing comprehensive input validation and output encoding measures that prevent the injection of malicious scripts. The application should sanitize all user-supplied input including the error parameter through proper encoding techniques such as HTML entity encoding before incorporating any user data into web responses. Additionally, implementing a content security policy that restricts script execution and employing proper parameter validation can effectively prevent this class of vulnerability from being exploited. Security teams should also consider implementing web application firewalls and regular security assessments to identify similar vulnerabilities that may exist in legacy web applications. The remediation process should involve thorough code review and the implementation of secure coding practices that align with industry standards including OWASP Top Ten recommendations for preventing cross-site scripting vulnerabilities.