CVE-2004-2491 in Web Browser
Summary
by MITRE
A race condition in Opera web browser 7.53 Build 3850 causes Opera to fill in the address bar before the page has been loaded, which allows remote attackers to spoof the URL in the address bar via the window.open and location.replace HTML parameters, which facilitates phishing attacks.
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Analysis
by VulDB Data Team • 01/22/2025
The vulnerability described in CVE-2004-2491 represents a critical race condition flaw in the Opera web browser version 7.53 build 3850 that fundamentally compromises user trust and security awareness. This issue stems from the browser's improper handling of navigation events where the address bar is populated with a URL before the corresponding page content has fully loaded, creating a window of opportunity for malicious actors to exploit this temporal inconsistency. The race condition occurs during the page loading lifecycle when the browser's rendering engine and navigation components are not properly synchronized, allowing attackers to manipulate the address bar display through specific HTML parameters.
The technical implementation of this vulnerability leverages the window.open and location.replace DOM methods to create misleading address bar content that does not accurately reflect the actual page being displayed. Attackers can craft malicious web pages that use these HTML parameters to redirect or open new windows with spoofed URLs, making it appear as though users are visiting legitimate websites when they are actually interacting with malicious content. This manipulation occurs because the browser's address bar update mechanism operates independently from the actual page loading process, creating a temporal gap where the displayed URL can be decoupled from the real page content. The flaw essentially allows attackers to present false visual cues to users, exploiting their natural trust in address bar information as a security indicator.
The operational impact of this vulnerability extends far beyond simple visual deception, as it directly enables sophisticated phishing attacks that can bypass user security awareness and traditional browser-based protections. Users who rely on address bar verification to confirm website legitimacy may be deceived into believing they are visiting trusted sites when they are actually interacting with malicious content. This vulnerability particularly affects users who are not security-aware or who do not actively monitor for signs of phishing, as the visual deception can be extremely convincing. The attack vector is particularly dangerous because it operates at the user interface level, making it difficult for traditional network-based security solutions to detect or prevent the deception, since the actual malicious content may be transmitted through legitimate network protocols.
This vulnerability aligns with CWE-362, which describes race conditions in software systems where the execution order of concurrent operations can lead to security flaws. The issue also maps to ATT&CK technique T1566.001, which covers spearphishing attacks through social engineering, as the ability to spoof address bar content significantly enhances the effectiveness of phishing campaigns. The flaw demonstrates how improper synchronization between user interface components and underlying system operations can create security vulnerabilities that are difficult to detect and prevent through conventional security measures. Organizations should consider implementing additional security awareness training to help users recognize such subtle phishing indicators and ensure that browser vendors maintain strict synchronization between UI updates and content loading processes.
Mitigation strategies for this vulnerability should include immediate browser updates to versions that address the race condition, as well as implementing additional security measures such as address bar validation techniques and enhanced user interface synchronization protocols. Browser vendors should ensure that address bar updates are strictly tied to actual page loading completion rather than being triggered by navigation events that may occur before content is fully rendered. Network security solutions should also be configured to monitor for suspicious URL patterns and browser behavior anomalies that may indicate exploitation attempts. Users should be educated about the importance of verifying website authenticity through multiple means beyond address bar content and should be trained to recognize potential phishing indicators such as unexpected redirects or unusual navigation patterns. The vulnerability highlights the critical importance of proper temporal synchronization in security-critical applications and demonstrates how seemingly minor implementation flaws can create significant security risks.