CVE-2005-2608 in SafeHTML
Summary
by MITRE
SafeHTML before 1.3.5 does not properly filter script in UTF-7 and CSS comments, which allows remote attackers to conduct cross-site scripting (XSS) attacks in vulnerable applications that use SafeHTML.
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Analysis
by VulDB Data Team • 07/10/2018
The vulnerability identified as CVE-2005-2608 affects SafeHTML versions prior to 1.3.5, representing a critical cross-site scripting weakness that exploits improper input sanitization mechanisms. This flaw specifically targets the filtering of script content within UTF-7 encoded data and CSS comment structures, creating a pathway for malicious actors to inject executable code into web applications that rely on SafeHTML for security protection. The vulnerability demonstrates a fundamental failure in the library's ability to properly handle internationalized character encodings and CSS parsing constructs, which are commonly encountered in modern web applications.
The technical implementation of this vulnerability stems from SafeHTML's inadequate processing of UTF-7 encoding, where malicious scripts can be concealed within UTF-7 encoded payloads that bypass standard filtering mechanisms. Additionally, the library fails to properly sanitize CSS comments, allowing attackers to embed malicious code within comment blocks that are subsequently rendered by web browsers. This dual weakness creates multiple attack vectors since both UTF-7 encoding and CSS comments are legitimate components of web content that applications commonly process and display. The vulnerability operates at the input validation layer, where the sanitization process does not account for these specific encoding and comment structures, enabling attackers to craft payloads that appear benign but contain executable code.
The operational impact of this vulnerability is significant as it allows remote attackers to execute arbitrary scripts within the context of victim browsers, potentially leading to session hijacking, credential theft, data manipulation, or redirection to malicious sites. The attack surface is broad since many web applications that utilize SafeHTML for input sanitization would be vulnerable, particularly those that process user-generated content or accept data from untrusted sources. The vulnerability is particularly dangerous because it can be exploited through seemingly innocuous inputs that contain UTF-7 encoded content or CSS comments, making detection and prevention challenging for security teams. This weakness directly violates the principle of least privilege and input validation, creating a persistent threat vector that can be leveraged for extended attack campaigns.
Mitigation strategies should prioritize immediate patching of SafeHTML to version 1.3.5 or later, which addresses the specific encoding and comment filtering issues. Organizations should implement comprehensive input validation that explicitly handles UTF-7 encoding and CSS comment structures, ensuring that all user-supplied content undergoes thorough sanitization regardless of encoding type. Security teams should also consider implementing additional layers of protection such as Content Security Policy headers, which can provide defense-in-depth against XSS attacks even if input validation fails. The vulnerability aligns with CWE-79 (Cross-site Scripting) and follows ATT&CK technique T1203 (Exploitation for Client Execution) where attackers leverage application vulnerabilities to execute malicious code. Organizations should conduct thorough code reviews to identify other instances where similar encoding or comment handling issues might exist, particularly in legacy applications that may use similar sanitization libraries. Regular security assessments should include testing for encoding-related vulnerabilities to prevent similar issues from emerging in other components of the application stack.