CVE-2008-0273 in Drupal
Summary
by MITRE
Interpretation conflict in Drupal 4.7.x before 4.7.11 and 5.x before 5.6, when Internet Explorer 6 is used, allows remote attackers to conduct cross-site scripting (XSS) attacks via invalid UTF-8 byte sequences, which are not processed as UTF-8 by Drupal s HTML filtering, but are processed as UTF-8 by Internet Explorer, effectively removing characters from the document and defeating the HTML protection mechanism.
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Analysis
by VulDB Data Team • 05/15/2025
The vulnerability described in CVE-2008-0273 represents a critical interpretation conflict within the Drupal content management system that specifically affects versions 4.7.x prior to 4.7.11 and 5.x prior to 5.6. This flaw exploits a fundamental discrepancy in how Drupal processes UTF-8 encoded data versus how Internet Explorer 6 interprets the same data, creating a pathway for malicious actors to bypass security measures designed to prevent cross-site scripting attacks. The vulnerability is particularly significant because it leverages the browser-specific behavior of Internet Explorer 6 to undermine Drupal's HTML filtering mechanisms, which are intended to sanitize user input and prevent malicious code execution.
The technical root cause of this vulnerability lies in the inconsistent handling of invalid UTF-8 byte sequences between Drupal's filtering system and Internet Explorer 6's rendering engine. When Drupal processes user input containing malformed UTF-8 sequences, it treats these sequences according to its own interpretation of UTF-8 encoding standards, which may not align with how Internet Explorer 6 processes the same sequences. This mismatch allows attackers to craft input that Drupal's HTML filter will accept and process without proper sanitization, while Internet Explorer 6 will interpret these same sequences in a way that removes characters from the document structure. This character removal effectively bypasses Drupal's security measures by creating a scenario where malicious code can be injected into the document without triggering the expected filtering behaviors.
The operational impact of this vulnerability extends beyond simple XSS attacks, as it demonstrates a fundamental flaw in how web applications handle character encoding discrepancies between different software components. Attackers can exploit this vulnerability by submitting specially crafted input containing invalid UTF-8 sequences that will be processed differently by the server-side filtering and the client-side browser rendering. This creates a situation where the HTML filter appears to successfully sanitize the input, but the actual rendered content in Internet Explorer 6 contains the malicious payload that was intended to be blocked. The vulnerability affects not just the security of individual Drupal installations but also highlights the broader challenges of maintaining consistent character encoding behavior across different software layers in web applications.
This vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws, and demonstrates how encoding-related issues can create security weaknesses that bypass traditional input validation mechanisms. The attack pattern follows typical XSS methodologies but utilizes encoding inconsistencies rather than direct injection techniques, making it particularly challenging to detect and prevent. Organizations using affected Drupal versions face significant risk as this vulnerability allows attackers to execute arbitrary JavaScript code in the context of users' browsers, potentially leading to session hijacking, data theft, or further exploitation of the compromised systems. The specific targeting of Internet Explorer 6 also reflects the historical challenges of supporting legacy browser versions while maintaining security standards, as older browsers often exhibit different security behaviors than modern implementations.
The recommended mitigations for this vulnerability include immediate upgrade to Drupal versions 4.7.11 or 5.6, which contain patches addressing the UTF-8 interpretation conflict. Additionally, administrators should implement comprehensive input validation and sanitization measures beyond the default Drupal filtering, particularly focusing on character encoding consistency checks. The vulnerability also underscores the importance of maintaining up-to-date software versions and the risks associated with supporting legacy browser environments. Organizations should conduct thorough security assessments to identify similar encoding discrepancies in their applications and implement robust testing procedures that verify consistent behavior across different software components and platforms. This vulnerability serves as a critical reminder of the complex interdependencies between different software layers and the importance of thorough testing across various execution environments to prevent encoding-related security issues.