CVE-2010-1585 in Thunderbird
Summary
by MITRE
The nsIScriptableUnescapeHTML.parseFragment method in the ParanoidFragmentSink protection mechanism in Mozilla Firefox before 3.5.17 and 3.6.x before 3.6.14, Thunderbird before 3.1.8, and SeaMonkey before 2.0.12 does not properly sanitize HTML in a chrome document, which makes it easier for remote attackers to execute arbitrary JavaScript with chrome privileges via a javascript: URI in input to an extension, as demonstrated by a javascript:alert sequence in (1) the HREF attribute of an A element or (2) the ACTION attribute of a FORM element.
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Analysis
by VulDB Data Team • 09/08/2021
The vulnerability identified as CVE-2010-1585 represents a critical security flaw in Mozilla Firefox and related applications that affects versions prior to specific patch releases. This issue resides within the nsIScriptableUnescapeHTML.parseFragment method, which is part of the ParanoidFragmentSink protection mechanism designed to sanitize HTML content. The flaw specifically impacts chrome documents, which are privileged documents that have access to sensitive browser functionality and can execute code with elevated privileges. When this mechanism fails to properly sanitize HTML input, it creates a pathway for attackers to inject malicious JavaScript code that can execute with chrome privileges, significantly elevating the potential impact of the attack.
The technical implementation of this vulnerability stems from improper handling of HTML sanitization within the browser's core rendering engine. The ParanoidFragmentSink protection mechanism was intended to prevent cross-site scripting attacks by sanitizing HTML content before it is processed, but a critical oversight occurred in how it handled javascript: URIs within specific HTML attributes. Attackers could exploit this by crafting malicious HTML input that contained javascript:alert sequences within either the HREF attribute of A elements or the ACTION attribute of FORM elements. When the browser processed these elements through the flawed parseFragment method, the sanitization process failed to properly neutralize the javascript: URI, allowing the embedded JavaScript code to execute with the privileges of the chrome document. This represents a classic case of insufficient input validation and sanitization where the protection mechanism itself became the point of failure.
The operational impact of this vulnerability is severe and far-reaching, as it allows remote attackers to execute arbitrary JavaScript code with chrome privileges, which are the highest level of privileges within the browser environment. Chrome privileges enable access to sensitive browser APIs, file system operations, and other privileged functions that normal web content cannot access. This means an attacker could potentially steal user data, modify browser behavior, install malware, or perform other malicious activities that would be impossible with standard web content privileges. The vulnerability is particularly dangerous because it can be triggered through browser extensions, which often have elevated privileges and can be easily exploited through social engineering or compromised extension repositories. The attack vector is straightforward - an attacker only needs to craft HTML content containing malicious javascript: URIs and either deliver it through a compromised website or through an extension that processes user input.
This vulnerability aligns with several established security frameworks and attack patterns. From a CWE perspective, it maps to CWE-79: Improper Neutralization of Input During Web Page Generation, which covers the failure to properly sanitize user input that can lead to code injection vulnerabilities. The attack pattern follows the ATT&CK framework's T1059.007 technique for Command and Scripting Interpreter: JavaScript, where attackers leverage JavaScript execution capabilities to perform malicious activities. Additionally, this vulnerability demonstrates characteristics of T1211: Exploitation for Privilege Escalation, where an initial foothold in a lower-privilege context is used to gain elevated privileges. The issue also reflects the broader category of T1555.003: Credentials from Password Stores, as the elevated privileges could potentially be used to access sensitive data or credentials stored within the browser environment. The vulnerability underscores the importance of proper input sanitization and the principle of least privilege in browser security architecture, where even protection mechanisms can become attack vectors if not properly implemented.
Mitigation strategies for this vulnerability require immediate patching of affected software versions, as the flaw exists in the core browser rendering engine and cannot be effectively addressed through configuration changes alone. Organizations should prioritize updating Firefox, Thunderbird, and SeaMonkey to versions 3.5.17, 3.6.14, 3.1.8, and 2.0.12 respectively, which contain the necessary fixes for the sanitization routine. Additionally, users should exercise extreme caution when installing browser extensions, as the vulnerability can be exploited through extension input processing. Network administrators should implement web filtering solutions to block known malicious domains and monitor for suspicious javascript: URI patterns in network traffic. The incident highlights the critical importance of maintaining up-to-date software and demonstrates how even security features designed to protect against attacks can themselves become attack vectors when implementation flaws exist. Security teams should also consider implementing browser security policies that restrict the execution of javascript: URIs in user-supplied content and establish regular security assessments of browser extension ecosystems to identify potential exploitation opportunities.