CVE-2010-1990 in Firefox
Summary
by MITRE
Mozilla Firefox 3.6.x, 3.5.x, 3.0.19, and earlier, and SeaMonkey, 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 • 02/05/2019
This vulnerability exists in Mozilla Firefox versions 3.6.x through 3.0.19 and SeaMonkey browsers where the mail application is automatically launched when an iframe element contains a mailto: URL in its src attribute. The flaw represents a classic case of improper input validation and resource management where the browser fails to properly handle multiple concurrent mailto: URI requests. When an attacker crafts an HTML document containing numerous iframe elements with mailto: URLs, the browser repeatedly triggers the mail application launch process, leading to resource exhaustion and ultimately causing a denial of service condition. The vulnerability stems from the browser's failure to implement proper rate limiting or request queuing mechanisms when processing multiple mailto: URI references within the same document context.
The technical implementation of this vulnerability involves the browser's handling of mailto: URI schemes within iframe contexts. When Firefox encounters an iframe with a mailto: URL in its source attribute, it automatically invokes the system's default mail application to process the URI. This behavior, while intended to provide seamless email functionality, becomes problematic when multiple iframe elements reference different mailto: URIs or when the same URI is referenced repeatedly. The browser's lack of proper throttling mechanisms means that each iframe element triggers a separate mail application launch, potentially overwhelming system resources and causing legitimate applications to become unresponsive. This issue falls under CWE-400, which specifically addresses "Uncontrolled Resource Consumption" and represents a denial of service vulnerability that can be exploited through excessive resource allocation.
The operational impact of this vulnerability extends beyond simple service disruption to potentially affect system stability and user productivity. An attacker can craft malicious HTML documents that, when loaded in vulnerable browsers, cause immediate and sustained resource consumption through repeated mail application launches. The denial of service occurs not only through the exhaustion of system resources but also through the blocking of legitimate mail application functionality, effectively preventing users from accessing their email clients. This vulnerability is particularly concerning in environments where users may be exposed to untrusted web content, as it can be exploited through simple web page loading without requiring any special privileges or user interaction beyond visiting the malicious site. The attack vector aligns with ATT&CK technique T1499.004, which covers "Endpoint Denial of Service" through resource exhaustion.
Mitigation strategies for this vulnerability involve both immediate browser updates and defensive programming practices. The primary solution is to upgrade to Firefox versions 3.6.20 or later and SeaMonkey versions 2.0.14 or later, which contain patches that address the improper handling of mailto: URIs within iframe contexts. Administrators should also implement content filtering measures that can identify and block HTML documents containing excessive iframe elements with mailto: URIs. Additionally, browser security policies should be configured to limit the automatic launching of external applications, particularly those that can be triggered through URI schemes. Network-level protections such as web application firewalls can also help detect and prevent exploitation attempts by monitoring for patterns of excessive iframe elements with mailto: URIs in incoming web traffic. The vulnerability demonstrates the importance of proper resource management in web browsers and highlights the need for robust input validation to prevent malicious exploitation of legitimate browser features.