CVE-2008-5511 in Firefox
Summary
by MITRE
Mozilla Firefox 3.x before 3.0.5 and 2.x before 2.0.0.19, Thunderbird 2.x before 2.0.0.19, and SeaMonkey 1.x before 1.1.14 allows remote attackers to bypass the same origin policy and conduct cross-site scripting (XSS) attacks via an XBL binding to an "unloaded document."
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 08/03/2021
The vulnerability described in CVE-2008-5511 represents a critical security flaw in Mozilla's browser and email client software that fundamentally undermines the browser's security model. This issue affects multiple Mozilla products including Firefox versions prior to 3.0.5 and 2.0.0.19, Thunderbird versions before 2.0.0.19, and SeaMonkey versions before 1.1.14. The vulnerability stems from a flaw in how these applications handle XBL (XML Binding Language) bindings within the context of unloaded documents, creating an avenue for attackers to circumvent the same origin policy that is fundamental to web security.
The technical flaw involves the improper handling of XBL bindings when documents are not yet fully loaded or rendered. XBL is a technology that allows developers to define reusable UI components and behaviors in XML format, and it can be used to extend the functionality of web documents. In the vulnerable versions, when an attacker constructs a malicious document containing XBL bindings that reference unloaded documents, the browser fails to properly enforce the same origin policy. This allows malicious code from one domain to access resources and execute operations on documents from different origins, effectively breaking down the security boundaries that prevent cross-site scripting attacks.
The operational impact of this vulnerability is severe as it enables attackers to perform sophisticated cross-site scripting attacks that would normally be prevented by browser security mechanisms. An attacker could craft malicious web pages that, when loaded in a victim's browser, would allow the execution of arbitrary code with the privileges of the victim's browser session. This could lead to session hijacking, data theft, credential compromise, and the ability to perform actions on behalf of the user against other websites. The vulnerability is particularly dangerous because it exploits a fundamental security mechanism rather than a specific application flaw, making it difficult to detect and prevent through traditional security measures.
This vulnerability aligns with CWE-94, which describes "Improper Control of Generation of Code ('Code Injection')" and is closely related to the ATT&CK technique T1059.001 for command and scripting interpreter. The flaw demonstrates how improper handling of dynamic content generation can lead to privilege escalation and arbitrary code execution. Organizations should implement immediate mitigations including prompt application updates to the patched versions, deployment of web application firewalls that can detect and block suspicious XBL binding patterns, and network-level controls that restrict access to known malicious domains. Additionally, security awareness training should emphasize the importance of keeping browser software updated and avoiding untrusted websites that may contain malicious XBL content. The vulnerability also highlights the importance of proper input validation and output encoding in web applications, as the flaw exists in the browser's interpretation of XML binding content rather than in the web application itself, making it a prime example of how browser security models must account for all possible attack vectors including those involving XML-based technologies and dynamic content loading mechanisms.