CVE-2015-2491 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 9 through 11 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted web site, aka "Memory Corruption Vulnerability," a different vulnerability than CVE-2015-2485 and CVE-2015-2541.
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Analysis
by VulDB Data Team • 06/14/2022
This vulnerability represents a critical memory corruption flaw affecting Microsoft Internet Explorer versions 9 through 11, classified under CWE-125 as out-of-bounds read conditions that can lead to arbitrary code execution. The vulnerability stems from improper handling of memory allocation and deallocation within the browser's rendering engine, specifically when processing malformed web content. Attackers can exploit this weakness by hosting malicious web pages that trigger buffer overflows or use after free conditions during object manipulation. The flaw operates at the intersection of multiple attack vectors including heap corruption and stack overflow scenarios that can be leveraged for privilege escalation. This vulnerability is particularly dangerous because it allows attackers to execute arbitrary code with the privileges of the logged-in user, making it a prime target for advanced persistent threats. The memory corruption occurs during the processing of specific JavaScript objects or DOM elements, where the browser fails to properly validate input data before performing memory operations. This weakness directly relates to ATT&CK technique T1059.007 for application execution through scripting and T1203 for legitimate user privileges exploitation. The vulnerability affects both Windows 7, 8, 8.1, and Server 2008 R2, 2012, 2012 R2 systems, creating a widespread attack surface across enterprise environments where legacy browser support is maintained.
The technical exploitation of this vulnerability involves crafting web content that triggers specific memory access patterns within Internet Explorer's JavaScript engine or core rendering components. Attackers typically leverage techniques such as heap spraying or use-after-free conditions to achieve code execution, where the corrupted memory is then manipulated to redirect program flow to malicious payload code. The flaw exists in the browser's handling of memory objects that are allocated and deallocated during normal web page processing, creating opportunities for attackers to overwrite critical memory regions. This type of vulnerability is particularly challenging to detect and mitigate because it often requires specific conditions to be met during memory allocation, making it difficult to reproduce in controlled environments. The memory corruption can manifest as either a crash leading to denial of service or as a more subtle corruption that allows for code execution. The vulnerability's classification as a remote code execution flaw means that no user interaction is required beyond visiting a malicious website, making it particularly dangerous for targeted attacks. The exploitation process typically involves multiple stages including initial memory corruption, followed by privilege escalation, and finally payload delivery. Security researchers have identified that the vulnerability is closely related to memory management functions within the browser's JavaScript engine, where improper bounds checking leads to unpredictable behavior.
The operational impact of CVE-2015-2491 extends beyond individual system compromise to affect entire enterprise networks, particularly those that maintain legacy Internet Explorer support for business-critical applications. Organizations running these vulnerable versions face significant risk of data breaches, system compromise, and potential lateral movement within their networks. The vulnerability's ability to cause denial of service attacks means that attackers can disrupt business operations by crashing browser sessions or entire systems. Enterprises that have not implemented proper patch management processes are particularly vulnerable to exploitation, as the vulnerability was patched in Microsoft security updates released in April 2015. The attack surface is further expanded by the fact that many organizations continue to support older browser versions for compatibility reasons, creating persistent attack vectors. This vulnerability demonstrates the importance of maintaining up-to-date security patches and implementing browser hardening measures. The impact is particularly severe in environments where users have administrative privileges, as successful exploitation can lead to complete system compromise. Organizations may experience increased security incidents, regulatory compliance issues, and potential financial losses due to data exposure or system downtime. The vulnerability also highlights the challenges of supporting legacy web technologies while maintaining security posture, as older browser versions often lack modern security features and protections.
Mitigation strategies for this vulnerability should include immediate patch deployment through Microsoft's security update channels, as the vulnerability was addressed through Microsoft Security Bulletin MS15-034. Organizations should implement browser hardening techniques such as disabling unnecessary browser features, implementing content security policies, and using sandboxing mechanisms to limit potential damage from exploitation attempts. Network-based mitigations include implementing web application firewalls and filtering malicious content at network boundaries, though these measures are not foolproof against sophisticated attacks. Security teams should also consider implementing user education programs to raise awareness about phishing attacks that may leverage this vulnerability. The implementation of automated patch management systems can help ensure timely deployment of security updates across enterprise environments. Additional protective measures include restricting Internet Explorer usage to trusted sites only, implementing strict browser configuration policies, and monitoring for anomalous network traffic that may indicate exploitation attempts. Organizations should also maintain comprehensive incident response plans that include procedures for handling browser-based security incidents, ensuring rapid detection and remediation of potential exploitation attempts. Regular security assessments and penetration testing can help identify systems that may still be running vulnerable versions of Internet Explorer, while continuous monitoring of threat intelligence feeds can provide early warning of potential exploitation attempts targeting this vulnerability.