CVE-2011-1246 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 8 does not properly handle content settings in HTTP responses, which allows remote web servers to obtain sensitive information from a different (1) domain or (2) zone via a crafted response, aka "MIME Sniffing Information Disclosure Vulnerability."
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Analysis
by VulDB Data Team • 03/19/2021
The vulnerability identified as CVE-2011-1246 represents a critical information disclosure flaw in Microsoft Internet Explorer 8 that exploits the browser's MIME sniffing behavior to enable cross-domain data exfiltration. This vulnerability stems from Internet Explorer's improper handling of content settings within HTTP responses, creating a pathway for malicious web servers to access sensitive information from different domains or security zones. The flaw specifically leverages the browser's automatic content type detection mechanism, which can be manipulated through carefully crafted HTTP responses to bypass normal security boundaries.
The technical implementation of this vulnerability involves Internet Explorer's MIME sniffing algorithm that attempts to determine the correct content type of received data by examining the actual content rather than relying solely on the Content-Type header provided by the server. When processing HTTP responses, IE8's content detection logic can be tricked into interpreting maliciously crafted responses in ways that expose information from other domains or zones. This occurs because the browser's security model does not adequately validate or constrain the content type detection process when dealing with cross-origin requests, allowing remote servers to manipulate the browser's interpretation of content in a manner that reveals sensitive data.
From an operational perspective, this vulnerability poses significant risks to enterprise environments where users may access multiple domains or security zones through a single browser instance. Attackers can exploit this flaw by hosting malicious web servers that craft HTTP responses designed to trigger IE8's MIME sniffing behavior, potentially gaining access to session cookies, authentication tokens, or other sensitive information that should normally be restricted to specific domains or zones. The attack vector is particularly dangerous because it requires no user interaction beyond visiting a malicious website, making it a passive information disclosure threat that can operate silently in the background.
The vulnerability aligns with CWE-200, which covers "Information Exposure," and demonstrates how improper input validation and content handling can lead to unauthorized information disclosure. From an ATT&CK framework perspective, this vulnerability maps to T1071.004 for Application Layer Protocol: DNS and T1566 for Phishing, as it enables attackers to craft sophisticated attacks that bypass traditional security controls through content manipulation. The flaw also relates to T1046 for Network Service Scanning, as attackers can use this vulnerability to probe for other domains and zones that may be accessible through the same browser instance.
Mitigation strategies for CVE-2011-1246 should focus on both immediate remediation and long-term security hardening. Microsoft released patches that addressed the specific MIME sniffing behavior that enabled this vulnerability, but organizations should also implement browser security policies that disable automatic content type detection where possible. Network administrators should consider deploying web application firewalls that can detect and block suspicious HTTP response patterns, while security teams should monitor for anomalous cross-domain requests that may indicate exploitation attempts. Additionally, user education regarding the risks of visiting untrusted websites and the importance of keeping browsers updated remains crucial for preventing successful exploitation of this vulnerability. The recommended approach includes implementing strict Content Security Policy headers, disabling unnecessary browser features that could be exploited, and maintaining comprehensive monitoring of network traffic for indicators of compromise related to this specific vulnerability pattern.