CVE-2008-4199 in Web Browser
Summary
by MITRE
Opera before 9.52 does not prevent use of links from web pages to feed source files on the local disk, which might allow remote attackers to determine the validity of local filenames via vectors involving "detection of JavaScript events and appropriate manipulation."
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Analysis
by VulDB Data Team • 05/25/2025
This vulnerability exists in Opera web browsers prior to version 9.52 and represents a significant information disclosure flaw that exploits the browser's handling of local file access through web page links. The vulnerability stems from Opera's insufficient validation of file paths when processing links that reference local disk resources, creating an attack vector that allows remote adversaries to probe local file system structures. The flaw specifically manifests when web pages attempt to reference feed source files located on the local disk, enabling attackers to exploit JavaScript event detection mechanisms to infer the existence or non-existence of specific local files. This represents a classic case of improper input validation and insufficient access control that violates fundamental security principles of web browser sandboxing.
The technical implementation of this vulnerability leverages JavaScript event handling capabilities within the Opera browser to detect whether specific local files are accessible or not. Attackers can construct malicious web pages that attempt to access predetermined local file paths and observe the browser's response through JavaScript event listeners that monitor file access attempts. When a file exists, the browser may trigger specific JavaScript events or return particular responses that differ from cases where files do not exist, allowing attackers to perform systematic enumeration of local file system structures. This technique exploits the browser's inconsistent handling of local file access attempts and the lack of proper sandboxing mechanisms that should prevent web content from determining local file system state. The vulnerability directly relates to CWE-20: Improper Input Validation and CWE-264: Permissions, Privileges and Access Controls, as it demonstrates insufficient validation of file access paths and inadequate access control mechanisms.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables attackers to perform reconnaissance activities that could lead to more sophisticated attacks. By determining the validity of local filenames, attackers can map out potentially sensitive file structures on the target system, identify installed software components, and locate configuration files or other resources that might contain sensitive information. This reconnaissance capability allows for targeted attacks against specific local applications or services that may be running on the system. The vulnerability also represents a potential stepping stone for privilege escalation attacks, as knowledge of local file system structure can inform subsequent exploitation attempts. From an attack framework perspective, this vulnerability aligns with ATT&CK technique T1083: File and Directory Discovery, as it enables adversaries to enumerate local file system resources without direct system access.
Organizations affected by this vulnerability should immediately implement browser updates to Opera version 9.52 or later, which contains the necessary patches to address the local file access validation issues. System administrators should also consider implementing additional network-level protections such as web application firewalls that can detect and block suspicious file access patterns from web content. Security monitoring should include detection of JavaScript-based file system enumeration attempts, particularly those involving local file access patterns that are typically restricted in secure browsing environments. The vulnerability highlights the importance of proper sandboxing mechanisms in web browsers and demonstrates how seemingly minor implementation flaws can result in significant security implications. Organizations should also conduct security assessments to ensure that other browsers and web-based applications do not exhibit similar vulnerabilities in their local file access handling mechanisms.