CVE-2001-0339 in Internet Explorer
Summary
by MITRE
Internet Explorer 5.5 and earlier allows remote attackers to display a URL in the address bar that is different than the URL that is actually being displayed, which could be used in web site spoofing attacks, aka the "Web page spoofing vulnerability."
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Analysis
by VulDB Data Team • 06/25/2021
The vulnerability identified as CVE-2001-0339 represents a significant web browser security flaw in Internet Explorer versions 5.5 and earlier that enabled malicious actors to manipulate user perception through address bar deception. This vulnerability operates by allowing attackers to craft web pages that display a misleading URL in the browser's address bar while simultaneously rendering different content that may appear to originate from a trusted source. The flaw stems from Internet Explorer's handling of certain HTML elements and URL parsing mechanisms that fail to properly validate or sanitize the display of web addresses during page rendering.
This technical weakness specifically exploits the browser's user interface presentation layer rather than underlying network protocols or core security mechanisms. The vulnerability occurs when Internet Explorer processes web content that contains specific combinations of HTML tags, JavaScript code, or URL formatting that manipulate the address bar display without corresponding changes to the actual page content being rendered. The flaw is particularly dangerous because it directly undermines user trust in the browser's address bar, which serves as the primary visual indicator of website authenticity and security status.
The operational impact of this vulnerability extends beyond simple deception to enable sophisticated phishing and social engineering attacks. Attackers can exploit this weakness to create convincing fake login pages or fraudulent websites that appear legitimate to users who rely on address bar verification. This capability significantly increases the success rate of web-based attacks by removing one of the primary defenses users employ to distinguish between authentic and malicious websites. The vulnerability particularly affects users who depend on visual cues from the address bar to verify site legitimacy, making it a prime target for financial fraud and credential theft operations.
Security researchers have classified this vulnerability under CWE-601 as an Open Redirect vulnerability, though the specific implementation in Internet Explorer 5.5 and earlier manifests as a user interface manipulation rather than traditional redirection. The ATT&CK framework categorizes this as a technique for "Masquerading" under the T1036 category, where adversaries use deceptive techniques to make their malicious activities appear legitimate to users. The vulnerability also aligns with T1566 in the ATT&CK matrix, representing a method for "Phishing" through deceptive web content presentation that exploits user trust in browser interface elements.
Mitigation strategies for this vulnerability primarily involve immediate browser updates to versions that properly address the address bar display handling, along with user education about verifying website authenticity through multiple indicators beyond just address bar content. Organizations should implement network-level controls such as URL filtering and content inspection systems to detect and block potentially malicious web content. Browser security configurations should be hardened to disable or restrict the execution of potentially malicious HTML elements and JavaScript code that could trigger this vulnerability. Additionally, users should be trained to verify SSL certificates and website authenticity through multiple verification methods rather than relying solely on address bar content, as the vulnerability specifically targets the trust users place in this interface element.