CVE-2004-2434 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 6.0 SP1 allows remote attackers to cause a denial of service (browser crash) via a link with "::{" (colon colon left brace), which triggers a null dereference when the user attempts to save the link using "Save As" and Internet Explorer prepares an error message with an attacker-controlled format string.
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Analysis
by VulDB Data Team • 07/28/2025
This vulnerability resides in Microsoft Internet Explorer 6.0 Service Pack 1 and represents a classic buffer overflow condition that manifests as a denial of service attack. The flaw occurs when a malicious web page contains a link with the specific sequence "::{" which triggers a null pointer dereference during the browser's attempt to process the link for saving. The vulnerability is categorized under CWE-125 as an out-of-bounds read condition that leads to application instability. When a user attempts to save such a link using the "Save As" functionality, Internet Explorer's internal error handling mechanism processes an attacker-controlled format string, causing the application to crash and terminate unexpectedly.
The technical exploitation of this vulnerability requires an attacker to craft a malicious webpage containing a link with the specific malformed sequence "::{". When a victim clicks this link and attempts to save it, the browser's handling of the malformed URI triggers a null pointer dereference in the Internet Explorer rendering engine. This type of vulnerability falls under the ATT&CK technique T1203 - Exploitation for Client Execution, where adversaries leverage browser vulnerabilities to execute malicious code or cause system instability. The vulnerability demonstrates a critical flaw in input validation and error handling within the browser's URI parsing mechanism.
The operational impact of this vulnerability extends beyond simple browser crashes, as it can be leveraged in social engineering campaigns where attackers craft convincing phishing pages designed to trigger the exploit. The attack vector requires user interaction through a web browser, making it particularly dangerous in environments where users frequently browse untrusted websites. Organizations with legacy Internet Explorer installations face significant risk as this vulnerability affects a widely deployed browser version that many enterprise environments still utilize. The exploit demonstrates how seemingly minor input validation flaws can result in complete application compromise and service disruption.
Mitigation strategies for this vulnerability include immediate deployment of Microsoft security patches and updates, as well as implementing browser hardening measures such as disabling unnecessary browser features and restricting user privileges when browsing. Organizations should consider implementing web application firewalls and content filtering solutions to prevent access to malicious websites containing such exploit vectors. The vulnerability also underscores the importance of regular security assessments and vulnerability management programs to identify and remediate similar flaws in legacy browser versions. Additionally, user education regarding safe browsing practices and the recognition of suspicious website elements remains crucial in preventing exploitation of such client-side vulnerabilities.