CVE-2015-6139 in Edge
Summary
by MITRE
Microsoft Internet Explorer 11 and Microsoft Edge mishandle content types, which allows remote attackers to execute arbitrary web script in a privileged context via a crafted web site, aka "Microsoft Browser Elevation of Privilege Vulnerability."
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Analysis
by VulDB Data Team • 06/29/2022
This vulnerability represents a critical elevation of privilege flaw affecting Microsoft Internet Explorer 11 and Microsoft Edge browsers. The issue stems from improper handling of content types within the browser's security model, creating a pathway for remote attackers to execute malicious scripts with elevated privileges. The vulnerability specifically targets the browser's content type processing mechanisms, which are responsible for determining how different types of web content should be interpreted and rendered. When these mechanisms fail to properly validate or sanitize content type headers, attackers can craft malicious websites that exploit this weakness to bypass normal security boundaries and gain access to privileged execution contexts. The flaw allows attackers to execute arbitrary web scripts in a privileged context, potentially enabling them to perform actions that should be restricted to system-level operations or administrative functions. This type of vulnerability falls under the category of content type confusion attacks, where the browser's interpretation of content headers leads to unexpected behavior in the execution environment. The security implications are severe as it undermines the fundamental security model that separates user-level web content from privileged system operations, effectively allowing attackers to escalate their privileges from regular web browsing to potentially system-level control.
The technical exploitation of this vulnerability leverages the browser's handling of content type headers and MIME type specifications that are sent by web servers to instruct browsers on how to process content. When Internet Explorer 11 and Microsoft Edge encounter malformed or specially crafted content type headers, they may incorrectly process the content, leading to privilege escalation. This behavior aligns with CWE-123, which addresses weaknesses in code that allow attackers to bypass security controls by manipulating input validation or processing logic. The vulnerability demonstrates a classic case of improper input validation where the browser's content type handling fails to properly sanitize or validate the content type information received from web servers. Attackers can craft web pages that contain specific content type headers designed to trigger the vulnerable code path, causing the browser to execute malicious JavaScript or other web scripts with elevated privileges. The exploitation process typically involves hosting a malicious website that sends crafted content type headers, which when processed by the vulnerable browser versions, trigger the privilege escalation mechanism. This attack vector represents a significant concern for enterprise environments where users may inadvertently visit compromised websites, potentially leading to full system compromise or unauthorized access to sensitive data and resources.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it can enable attackers to perform a wide range of malicious activities that would normally be restricted. Successful exploitation could allow attackers to install malware, modify system configurations, access sensitive files, or even take complete control of affected systems. The vulnerability affects both Internet Explorer 11 and Microsoft Edge, representing a broad attack surface that includes both legacy and modern browser versions. Organizations using these browsers are particularly at risk as the vulnerability can be exploited through standard web browsing activities without requiring any special user interaction beyond visiting a malicious website. The attack can be executed remotely through web-based delivery mechanisms, making it particularly dangerous for enterprise environments where users frequently access external websites. This vulnerability also aligns with several ATT&CK tactics including privilege escalation and defense evasion, as attackers can use the elevated privileges to avoid detection and maintain persistent access. The potential for widespread impact exists because the vulnerability affects major Microsoft browser products that are widely deployed across enterprise and consumer environments. The risk is compounded by the fact that many users may not be aware of the specific attack vectors, making them more susceptible to exploitation through social engineering or drive-by download scenarios.
Mitigation strategies for this vulnerability should include immediate patching of affected systems with the relevant Microsoft security updates. Organizations should implement browser hardening measures such as disabling unnecessary browser features, implementing content security policies, and configuring security settings to reduce the attack surface. Network-based mitigations can include implementing web application firewalls and content filtering solutions that can detect and block malicious content type headers. Regular security assessments should be conducted to identify systems running vulnerable browser versions and ensure timely patch deployment. Security monitoring should be enhanced to detect suspicious browser behavior or attempts to exploit content type handling vulnerabilities. The implementation of multi-factor authentication and least privilege access controls can help limit the potential damage if exploitation occurs. Additionally, user education programs should be established to raise awareness about the risks of visiting untrusted websites and the importance of keeping browsers updated. Organizations should also consider implementing browser isolation techniques or using alternative browser security models that provide better protection against content type manipulation attacks. Regular vulnerability scanning and penetration testing should be performed to identify any remaining exposure points and ensure that mitigation measures are effective against this specific vulnerability. The remediation process should include comprehensive testing of patches in controlled environments before deployment to production systems to avoid potential compatibility issues or service disruptions.