CVE-2008-4723 in Firefox
Summary
by MITRE
Multiple cross-site scripting (XSS) vulnerabilities in Mozilla Firefox 3.0.1 through 3.0.3 allow remote attackers to inject arbitrary web script or HTML via an ftp:// URL for an HTML document within a (1) JPG, (2) PDF, or (3) TXT file. NOTE: the provenance of this information is unknown; the details are obtained solely from third party information.
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Analysis
by VulDB Data Team • 08/19/2019
This vulnerability represents a critical cross-site scripting flaw in mozilla firefox versions 3.0.1 through 3.0.3 that demonstrates how seemingly innocuous file type handling can create significant security risks. The vulnerability specifically targets the browser's interpretation of html content embedded within certain file types when accessed via ftp protocol, creating a pathway for remote attackers to execute malicious scripts. The attack vector involves constructing malicious ftp urls that point to html documents contained within jpg pdf or txt files, exploiting firefox's content type detection and rendering mechanisms. This represents a classic case of improper input validation where the browser fails to properly sanitize file content based on the file extension or content type, allowing attackers to bypass security controls that would normally prevent script execution.
The technical flaw stems from firefox's inadequate handling of html content within non-html file types when accessed through ftp protocol. When users navigate to ftp urls that point to html documents embedded within image or document files, the browser's content detection logic incorrectly processes these resources, leading to script execution in the context of the user's browsing session. This behavior violates fundamental security principles around content type validation and privilege separation. The vulnerability operates at the application layer and demonstrates how protocol handling can create unexpected execution paths. According to CWE classification, this maps to CWE-79 which describes cross-site scripting vulnerabilities, and the specific implementation flaw aligns with CWE-117 which addresses improper output neutralization for logs. The attack requires no special privileges beyond the ability to create or control ftp content, making it particularly dangerous in environments where users might encounter malicious ftp links.
The operational impact of this vulnerability extends beyond simple script injection, as it allows attackers to perform session hijacking, steal cookies, redirect users to malicious sites, and potentially execute arbitrary commands on victim systems. The attack requires victims to navigate to specifically crafted ftp urls, but once executed, the malicious scripts run with the privileges of the victim's browser session. This creates a significant risk for users who browse ftp sites or encounter malicious ftp links in emails or web pages. The vulnerability's impact is amplified by the fact that it affects a widely used browser and can be exploited through various file types, increasing the attack surface. From an att&ck framework perspective, this vulnerability maps to tactic TA0001 (initial access) and technique T1190 (exploitation of remote services) with potential progression to T1078 (valid accounts) and T1531 (steal application access token). The attack chain relies on user interaction and demonstrates how browser-based vulnerabilities can be leveraged for broader compromise.
Mitigation strategies for this vulnerability require immediate browser updates to patched versions that properly handle content type detection for ftp resources. Users should avoid navigating to untrusted ftp sites and should disable automatic content type detection for ftp resources when possible. Organizations should implement network-level controls to restrict ftp access where possible and deploy web application firewalls that can detect and block malicious script patterns. The vulnerability highlights the importance of proper content type validation and demonstrates why security updates must be applied promptly. Browser vendors should implement more robust sandboxing mechanisms and content validation controls to prevent similar issues in the future. Additionally, users should be educated about the risks of clicking on suspicious links and should verify the legitimacy of ftp resources before accessing them. The vulnerability underscores the need for comprehensive security testing that includes protocol handling and content type detection scenarios, as well as the importance of maintaining up-to-date security patches across all browser versions.