CVE-2004-2307 in Windows
Summary
by MITRE
Microsoft Internet Explorer 6.0.2600 on Windows XP allows remote attackers to cause a denial of service (browser crash) via a shell: URI with double backslashes (\\) in an HTML tag such as IFRAME or A.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 06/18/2017
This vulnerability exists in Microsoft Internet Explorer 6.0.2600 running on Windows XP systems where the browser fails to properly handle shell: URI schemes containing double backslashes in HTML tags. The flaw stems from improper input validation and parsing of URI schemes within HTML elements, specifically when processing iframe and anchor tags that contain shell: URIs with malformed path components. The vulnerability is classified under CWE-129 as an input validation issue where the application does not adequately sanitize or validate URI components before processing them. When a maliciously crafted HTML page containing a shell: URI with double backslashes is loaded, the browser's URI parsing mechanism becomes overwhelmed and crashes, resulting in a complete denial of service condition that affects the user's browsing session.
The technical exploitation occurs when an attacker crafts an HTML page that includes an iframe or anchor tag referencing a shell: URI containing double backslashes in the path portion of the URI. The browser's handling of these malformed URIs causes memory corruption or stack overflow conditions during the URI resolution process, leading to an unhandled exception that terminates the browser process. This vulnerability specifically affects the URL parsing component of Internet Explorer's web rendering engine and represents a classic buffer overflow scenario where improper input handling leads to application instability. The issue demonstrates a failure in the browser's URI scheme validation logic that should have rejected or properly escaped the malformed URI components before attempting to process them.
The operational impact of this vulnerability extends beyond simple browser crashes as it can be leveraged in phishing attacks or social engineering campaigns where users are tricked into visiting malicious websites. Attackers can craft convincing web pages that appear legitimate while containing the malicious URI constructs, leading to unexpected browser termination that may be exploited to confuse users or disrupt their browsing sessions. The vulnerability affects a broad user base since IE6 was widely deployed on Windows XP systems, making it particularly dangerous in enterprise environments where legacy systems remain operational. This type of denial of service attack can also be used as a preliminary step in more sophisticated attacks, as it may be used to establish a foothold or to create distractions during larger exploitation attempts.
Mitigation strategies for this vulnerability include applying the relevant Microsoft security patch that addresses the URI parsing flaw in Internet Explorer 6.0.2600, implementing network-level filtering to block shell: URI schemes, and deploying web application firewalls that can detect and block malicious URI patterns. Organizations should also consider implementing user education programs to raise awareness about suspicious web content and encourage safe browsing practices. From an ATT&CK framework perspective, this vulnerability aligns with techniques such as T1210 (Exploitation of Remote Services) and T1499 (Endpoint Denial of Service) as it enables attackers to cause system instability through remote code execution. Additionally, organizations should consider implementing browser hardening measures such as disabling unnecessary URI schemes, restricting JavaScript execution, and implementing content security policies to prevent the loading of potentially malicious content. The vulnerability also highlights the importance of proper input validation and the need for robust URI parsing mechanisms that can handle malformed inputs without crashing the application.