CVE-2007-0994 in Firefox
Summary
by MITRE
A regression error in Mozilla Firefox 2.x before 2.0.0.2 and 1.x before 1.5.0.10, and SeaMonkey 1.1 before 1.1.1 and 1.0 before 1.0.8, allows remote attackers to execute arbitrary JavaScript as the user via an HTML mail message with a javascript: URI in an (1) img, (2) link, or (3) style tag, which bypasses the access checks and executes code with chrome privileges.
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Analysis
by VulDB Data Team • 07/16/2019
This vulnerability represents a critical security flaw in Mozilla Firefox and SeaMonkey web browsers that stems from a regression error in the handling of javascript: URIs within HTML email messages. The issue affects multiple browser versions including Firefox 2.x before 2.0.0.2 and 1.x before 1.5.0.10, along with SeaMonkey 1.1 before 1.1.1 and 1.0 before 1.0.8, creating a significant attack surface for remote code execution. The vulnerability specifically targets the browser's security model by exploiting how it processes javascript: URIs within different HTML tags, allowing attackers to bypass normal access controls and execute malicious code with elevated chrome privileges that typically should be restricted to privileged browser components.
The technical mechanism behind this vulnerability involves the improper handling of javascript: URIs when they appear within img, link, or style HTML tags in HTML email content. When a user opens an email containing such malicious content, the browser's security checks fail to properly validate or sanitize these URIs, allowing the javascript code to execute in a context that should normally be restricted. This regression error essentially removes the security boundaries that should prevent untrusted content from executing with the privileges of the browser's chrome layer, which has access to sensitive system functions and user data. The flaw operates at the core of the browser's URI processing and privilege escalation mechanisms, creating a pathway for attackers to execute arbitrary JavaScript code that would normally be blocked by the browser's security architecture.
The operational impact of this vulnerability is severe as it enables remote code execution with chrome privileges, meaning attackers can potentially access sensitive user data, manipulate browser functionality, and perform actions that should be restricted to the browser's privileged components. This type of vulnerability falls under CWE-264, which addresses permissions, privileges, and access controls, and aligns with ATT&CK technique T1059.007 for command and scripting interpreter. The ability to execute code with chrome privileges provides attackers with extensive capabilities including but not limited to stealing cookies, accessing local files, modifying browser behavior, and potentially escalating to full system compromise. The vulnerability is particularly dangerous in email contexts where users often trust content from known senders, making social engineering attacks more effective.
Mitigation strategies for this vulnerability require immediate patching of affected browser versions to address the regression error in URI handling and privilege escalation checks. Organizations should implement email filtering solutions that can detect and block HTML content containing javascript: URIs in img, link, or style tags, while also ensuring users are educated about the risks of opening suspicious email attachments. Security professionals should consider implementing browser security policies that restrict javascript execution in email contexts and monitor for unusual privilege escalation attempts. The fix typically involves restoring proper access controls and URI validation mechanisms that prevent javascript: URIs from executing with elevated privileges, aligning with security best practices for preventing privilege escalation attacks and maintaining proper separation of privileges between user content and browser components.