CVE-2004-0259 in Formmail.php
Summary
by MITRE
The check_referer() function in Formmail.php 5.0 and earlier allows remote attackers to bypass access restrictions via an empty or spoofed HTTP Referer, as demonstrated using an application on the same web server that contains a cross-site scripting (XSS) issue.
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Analysis
by VulDB Data Team • 06/22/2018
The vulnerability identified as CVE-2004-0259 represents a critical access control flaw in the Formmail.php script version 5.0 and earlier, where the check_referer() function fails to properly validate incoming HTTP Referer headers. This weakness stems from the script's reliance on the Referer header for access restriction enforcement, a mechanism that can be easily manipulated by malicious actors. The vulnerability specifically affects web applications that utilize the Formmail.php script for processing form submissions, creating a potential pathway for unauthorized access to sensitive functionality.
The technical flaw resides in the inadequate validation of HTTP Referer headers within the check_referer() function, which accepts empty or spoofed headers as valid inputs. This design flaw allows attackers to bypass the intended access controls by simply omitting the Referer header or crafting a falsified one that appears to originate from an authorized domain. The vulnerability becomes particularly dangerous when combined with existing cross-site scripting issues on the same web server, as demonstrated in the original exploit scenario. Attackers can leverage this weakness to execute malicious code through the Formmail.php script, potentially gaining unauthorized access to restricted features or data.
The operational impact of this vulnerability extends beyond simple access bypass, as it can enable a range of malicious activities including data exfiltration, privilege escalation, and unauthorized form submissions. When combined with other vulnerabilities on the same server, such as XSS flaws, the attack surface expands significantly, allowing for more sophisticated exploitation techniques. The vulnerability affects web applications that depend on the Formmail.php script for email form processing, potentially compromising entire web applications or entire server environments depending on how the script is integrated.
The security implications of CVE-2004-0259 align with CWE-284, which addresses improper access control issues, and can be mapped to ATT&CK technique T1213.002 for data from information repositories. Organizations using vulnerable versions of Formmail.php face significant risk of unauthorized access to their web application functionality, particularly when the script is deployed in environments with other security weaknesses. The vulnerability demonstrates the importance of robust input validation and the dangers of relying on headers that can be easily manipulated by attackers, highlighting the need for more secure authentication and authorization mechanisms.
Mitigation strategies should focus on implementing proper input validation for all HTTP headers, including the Referer header, and replacing the vulnerable check_referer() function with more robust authentication mechanisms. Organizations should upgrade to patched versions of Formmail.php or implement additional access control measures such as token-based authentication, IP address restrictions, or server-side validation that does not rely on potentially manipulable HTTP headers. The vulnerability serves as a reminder of the critical importance of secure coding practices and the need for comprehensive security testing that considers the interaction between multiple vulnerabilities within the same application ecosystem. Regular security audits and vulnerability assessments should be conducted to identify and remediate similar issues in other web applications that may be relying on similar flawed access control mechanisms.