CVE-2010-1991 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 6.0.2900.2180, 7, and 8.0.7600.16385 executes a mail application in situations where an IFRAME element has a mailto: URL in its SRC attribute, which allows remote attackers to cause a denial of service (excessive application launches) via an HTML document with many IFRAME elements.
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Analysis
by VulDB Data Team • 09/14/2021
This vulnerability in Microsoft Internet Explorer represents a classic denial of service flaw that exploits the browser's handling of mailto: URLs within IFRAME elements. The issue affects versions 6.0.2900.2180, 7, and 8.0.7600.16385, where the browser's automatic execution of mail applications when encountering mailto: URLs in IFRAME SRC attributes creates a dangerous execution pattern. When an HTML document contains multiple IFRAME elements referencing mailto: URLs, the browser triggers the default mail application for each instance, leading to a cascade of application launches that can overwhelm system resources. This behavior violates the principle of least privilege and demonstrates poor input validation in the browser's URL handling mechanism.
The technical flaw stems from the browser's insufficient sanitization of IFRAME SRC attributes when they contain mailto: protocols. According to CWE-444, this vulnerability maps to improper input validation where the application fails to properly validate or sanitize input before processing. The vulnerability operates at the application layer of the OSI model, specifically within the browser's rendering engine where HTML parsing and URL resolution occur. The flaw allows for arbitrary execution of the system's default mail client without user interaction, making it particularly dangerous in malicious web page contexts. This issue is classified under the ATT&CK technique T1203 - Exploitation for Client Execution, where adversaries leverage browser vulnerabilities to execute malicious code or cause system instability.
The operational impact of this vulnerability extends beyond simple resource exhaustion, as it can be exploited to disrupt normal user operations and potentially serve as a stepping stone for more sophisticated attacks. When multiple IFRAME elements with mailto: URLs are present in a single document, the cascading effect can result in dozens or even hundreds of mail application instances launching simultaneously, consuming significant system memory and processor resources. This can lead to complete system unresponsiveness or forced application crashes, effectively creating a denial of service condition that prevents legitimate users from accessing the affected system. The vulnerability is particularly concerning in enterprise environments where users may inadvertently visit malicious websites, as it can be used to disrupt business operations and productivity. Organizations should implement browser hardening measures and consider deploying web application firewalls to prevent exploitation of this vulnerability. The flaw also highlights the importance of proper sandboxing mechanisms and input validation in browser implementations to prevent such cascading execution scenarios.