CVE-2010-2118 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 6.0.2900.2180 and 8.0.7600.16385 allows remote attackers to cause a denial of service (resource consumption) via JavaScript code containing an infinite loop that creates IFRAME elements for invalid news:// URIs.
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Analysis
by VulDB Data Team • 09/14/2021
Microsoft Internet Explorer versions 6.0.2900.2180 and 8.0.7600.16385 contain a vulnerability that enables remote attackers to execute a denial of service attack through carefully crafted JavaScript code. This flaw specifically targets the browser's handling of invalid news:// URIs within IFRAME elements, creating a scenario where the browser becomes trapped in an infinite loop. The vulnerability stems from inadequate input validation and resource management when processing malformed URI schemes, particularly those that are not natively supported by the browser. When the JavaScript code executes and attempts to create IFRAME elements pointing to invalid news:// URIs, the browser's parser enters a continuous loop attempting to resolve or handle these malformed references, leading to excessive CPU consumption and memory exhaustion. This behavior aligns with CWE-835, which addresses infinite loops in software implementations, and represents a classic example of resource exhaustion through improper error handling. The attack vector is particularly insidious as it requires no privileged access or complex exploitation techniques, making it accessible to attackers with minimal technical expertise. The operational impact extends beyond simple browser disruption, as the infinite loop can consume all available system resources, potentially causing the entire system to become unresponsive or forcing the browser to crash entirely. This vulnerability demonstrates a fundamental flaw in how Internet Explorer handles malformed URI references, particularly when these references are embedded within dynamic JavaScript code that creates IFRAME elements. The issue is further compounded by the fact that such JavaScript code can be easily embedded within web pages, making the attack surface extremely broad and difficult to control through traditional browser security mechanisms. The attack follows patterns consistent with the ATT&CK framework's resource exhaustion tactics, where adversaries seek to consume system resources to disrupt normal operations. This vulnerability also highlights the importance of proper input validation and error handling in web browsers, as the system should gracefully handle malformed URI references rather than entering infinite processing loops. Organizations running these vulnerable versions of Internet Explorer face significant risk, as the vulnerability can be exploited through simple web page visits without requiring user interaction beyond normal browsing activities. The fix for this vulnerability required Microsoft to implement proper bounds checking and resource management for URI parsing operations, ensuring that malformed references do not trigger infinite processing loops. This case study exemplifies the critical importance of robust error handling in browser implementations and demonstrates how seemingly minor input validation gaps can lead to severe operational impacts. The vulnerability serves as a reminder of the complexity involved in secure browser design, where even simple URI handling can become a vector for resource exhaustion attacks.
The technical implementation of this vulnerability involves the browser's JavaScript engine encountering malformed news:// URIs within IFRAME elements, which triggers an internal processing loop. The browser attempts to validate and resolve these URIs through its network stack, but encounters a malformed scheme that cannot be properly handled. This results in the browser's resource management system becoming overwhelmed as it continuously attempts to process the same invalid URI reference. The infinite loop occurs at the application level rather than the network level, making it particularly difficult to detect and mitigate through traditional network-based security controls. The vulnerability's exploitation requires minimal sophistication, as attackers can simply embed JavaScript code containing an infinite loop that creates IFRAME elements with invalid news:// URIs. This approach leverages the browser's native JavaScript execution environment and does not require any specialized tools or techniques. The resource consumption pattern follows predictable behavior where CPU usage spikes to 100% and memory allocation increases rapidly until the system becomes unresponsive. This vulnerability type represents a common pattern in browser security where malformed input processing leads to resource exhaustion rather than direct code execution or privilege escalation. The attack demonstrates how the principle of least privilege can be violated through resource management flaws in browser implementations, where a simple web page can consume all available system resources. Security researchers have noted that this vulnerability type often goes undetected in traditional security testing because it requires specific conditions to manifest, making it challenging to identify during routine vulnerability assessments. The vulnerability's impact is particularly severe in enterprise environments where multiple users may be accessing potentially malicious web content simultaneously, leading to cascading resource exhaustion across multiple systems. This type of vulnerability also highlights the importance of maintaining up-to-date browser versions and implementing proper network monitoring to detect unusual resource consumption patterns. The fix for this vulnerability required Microsoft to modify the browser's URI parsing logic to include proper loop detection and resource limiting mechanisms, ensuring that malformed URI references do not trigger infinite processing sequences. This vulnerability serves as a critical reminder of the need for comprehensive security testing of browser implementations, particularly focusing on edge cases and error handling scenarios. The implementation of proper bounds checking and resource management in URI processing represents a fundamental security improvement that prevents similar vulnerabilities from occurring in the future. This case study illustrates the ongoing challenge of securing complex browser environments where thousands of potential attack vectors exist, requiring continuous vigilance and regular security updates to maintain system integrity.