CVE-2012-6502 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer before 10 allows remote attackers to obtain sensitive information about the existence of files, and read certain data from files, via a UNC share pathname in the SRC attribute of a SCRIPT element, as demonstrated by reading a name-value pair from a local file via a \\127.0.0.1\C$\ sequence.
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Analysis
by VulDB Data Team • 12/21/2021
This vulnerability in Microsoft Internet Explorer versions prior to 10 represents a critical information disclosure flaw that exploits the browser's handling of UNC (Universal Naming Convention) paths within SCRIPT element attributes. The vulnerability specifically affects how Internet Explorer processes file paths when the SRC attribute of a SCRIPT element contains a UNC share pathname, creating an unintended code execution pathway that can be leveraged by remote attackers to access local system resources. The flaw manifests when a malicious web page attempts to load a script from a UNC path, allowing the browser to connect to remote file shares and potentially read local files through the network protocol implementation. This vulnerability directly relates to CWE-200, which addresses information exposure, and specifically targets the improper handling of file paths and network resource access within web browsers.
The technical exploitation occurs when Internet Explorer attempts to resolve a SCRIPT element's SRC attribute containing a UNC path such as \\127.0.0.1\C$\, which allows an attacker to construct malicious web pages that can access local files on the victim's system. The browser's network stack processes these UNC paths without proper validation, enabling the retrieval of sensitive information from local files through network protocols. This represents a privilege escalation vulnerability where a remote attacker can gain unauthorized access to local file systems, potentially reading configuration files, user data, or other sensitive information stored on the compromised system. The vulnerability can be exploited across network boundaries and does not require local system access from the attacker, making it particularly dangerous in enterprise environments where network segmentation is expected.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable more sophisticated attacks by providing attackers with knowledge of local file structures and potentially sensitive data contained within those files. Attackers can use this vulnerability to map local network shares, identify system configuration files, or extract user credentials stored in local files, significantly expanding their attack surface. The vulnerability also aligns with ATT&CK technique T1059.001, which covers command and scripting interpreter usage, as the exploitation involves the execution of script content through malformed path references. Additionally, this flaw can be combined with other techniques to create more complex attack chains, potentially leading to full system compromise through information gathering and reconnaissance phases.
Organizations should implement immediate mitigations including updating Internet Explorer to version 10 or later, where this vulnerability has been addressed through proper validation of UNC paths and enhanced network resource access controls. Network administrators should also consider implementing firewall rules to block outbound connections to local network shares and restrict access to UNC paths from web browsers. The vulnerability demonstrates the importance of proper input validation and the dangers of allowing web browsers to directly access local file system resources through network protocols. Security teams should monitor for exploitation attempts and consider implementing web application firewalls to detect and block requests containing suspicious UNC path patterns. Additionally, user education regarding the risks of visiting untrusted websites and the importance of keeping browser software updated remains critical in preventing exploitation of this class of vulnerability.