CVE-2006-3227 in Internet Explorer
Summary
by MITRE
Interpretation conflict between Internet Explorer and other web browsers such as Mozilla, Opera, and Firefox might allow remote attackers to modify the visual presentation of web pages and possibly bypass protection mechanisms such as content filters via ASCII characters with the 8th bit set, which could be stripped by Internet Explorer to render legible text, but not when using other browsers. NOTE: there has been significant discussion about this issue, and as of 20060625, it is not clear where the responsibility for this issue lies, although it might be due to vagueness within the associated standards. NOTE: this might only be exploitable with certain encodings.
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Analysis
by VulDB Data Team • 04/07/2017
This vulnerability represents a critical cross-browser compatibility issue that emerged from fundamental disagreements in how web browsers interpret and process character encoding standards. The core problem stems from inconsistent handling of ASCII characters with the 8th bit set, which are often used in various encoding schemes including iso-8859-1 and windows-1252. Internet Explorer demonstrated a specific behavior where it would strip or modify these high-bit characters during rendering, while other browsers like Mozilla Firefox, Opera, and Safari maintained the original character values. This divergence creates a potential attack surface where malicious actors could craft web content that appears normal in non-IE browsers but behaves differently when viewed in Internet Explorer, potentially exposing security mechanisms that rely on character-based filtering or validation.
The technical flaw manifests in the way browsers process character encoding during HTML parsing and rendering phases. When a web page contains UTF-8 or other multi-byte encoded content, Internet Explorer's parser may interpret the 8th bit set characters differently than other browsers, leading to inconsistent rendering behavior. This inconsistency can be exploited to bypass content filtering systems that assume uniform character processing across all browsers. The vulnerability particularly affects web applications that implement security controls based on character validation or filtering, where the same input might be processed differently depending on the user's browser choice. The issue becomes more pronounced when dealing with specific encodings such as iso-8859-1 or windows-1252, where the 8th bit characters have defined meanings in those standards but may be interpreted differently by Internet Explorer's legacy parsing engine.
The operational impact of this vulnerability extends beyond simple visual presentation issues to potentially serious security implications. Attackers could craft malicious web content that appears benign in modern browsers but triggers unintended behavior in Internet Explorer, potentially bypassing security filters or content validation mechanisms. This creates a scenario where a web application might be protected against attacks in one browser but remain vulnerable in another, effectively creating a false sense of security for users who might be using different browsers. The vulnerability particularly affects enterprise environments where users might have mixed browser configurations, or where security policies are based on assumptions about uniform browser behavior. Additionally, this issue can complicate web application security testing and validation, as security controls might pass tests in some browsers but fail in others, leading to potential gaps in protection.
The root cause of this vulnerability aligns with CWE-1321, which addresses issues related to inconsistent handling of character encoding across different systems or components. This type of interpretation conflict represents a broader category of problems in web standards implementation where different vendors may interpret the same specification differently, leading to security and compatibility issues. From an ATT&CK perspective, this vulnerability could be categorized under T1071.001 Application Layer Protocol and T1566.001 Phishing, as it enables attackers to craft content that bypasses security controls and potentially deceives users through visual manipulation. The vulnerability's exploitation requires understanding of browser-specific encoding behaviors and character set handling, making it particularly challenging to defend against through traditional security measures. Organizations should implement comprehensive browser compatibility testing and consider using standardized character encoding practices that minimize the risk of such interpretation conflicts. The vulnerability also underscores the importance of adhering to well-defined web standards and the potential security implications of deviating from established protocols, particularly in environments where multiple browser vendors' implementations interact with security-sensitive applications.