CVE-2016-5166 in Chrome
Summary
by MITRE
The download implementation in Google Chrome before 53.0.2785.89 on Windows and OS X and before 53.0.2785.92 on Linux does not properly restrict saving a file:// URL that is referenced by an http:// URL, which makes it easier for user-assisted remote attackers to discover NetNTLM hashes and conduct SMB relay attacks via a crafted web page that is accessed with the "Save page as" menu choice.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 09/14/2022
The vulnerability described in CVE-2016-5166 represents a critical security flaw in Google Chrome's file download handling mechanism that existed across multiple operating systems. This issue specifically affected Chrome versions prior to 53.0.2785.89 on Windows and OS X, and before 53.0.2785.92 on Linux, creating a significant attack surface for remote threat actors. The flaw resides in how Chrome processes file:// URLs that are referenced by http:// URLs during the "Save page as" operation, allowing attackers to exploit this behavior for credential harvesting and network-based attacks.
The technical implementation of this vulnerability stems from insufficient validation of file paths when handling web content that references local files. When a user accesses a malicious web page containing a crafted file:// URL that references a local resource, Chrome's download mechanism fails to properly restrict the saving operation. This improper restriction allows attackers to manipulate the download process to access local network resources and potentially capture authentication credentials. The vulnerability specifically enables attackers to conduct SMB relay attacks by leveraging the NetNTLM hash collection mechanism, which occurs when Chrome attempts to resolve the referenced file path through network protocols.
The operational impact of this vulnerability extends beyond simple credential theft, as it provides attackers with a pathway for lateral movement within network environments. When users save pages containing malicious file references, the browser's handling of these URLs can inadvertently expose local network resources and authentication mechanisms to remote attackers. This creates opportunities for attackers to harvest NetNTLM hashes, which can then be used in pass-the-hash attacks or relayed to other systems within the network. The vulnerability is particularly dangerous because it requires minimal user interaction beyond visiting a malicious webpage and selecting the "Save page as" option, making it a prime candidate for user-assisted remote attacks.
The security implications of CVE-2016-5166 align with CWE-22, which addresses improper limitation of a pathname to a restricted directory, and also relates to CWE-352, covering cross-site request forgery vulnerabilities. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access through network protocols and privilege escalation via relay attacks. The attack vector leverages the browser's trust model and download handling capabilities to bypass normal network security controls, making it particularly effective against environments where users have elevated privileges or where network segmentation is insufficient. Organizations should consider this vulnerability as part of broader attack chains that could lead to full system compromise, especially in environments where SMB authentication is prevalent and network monitoring is inadequate.
Mitigation strategies for this vulnerability require immediate patching of affected Chrome versions to ensure proper path validation and download restrictions. Security teams should implement network monitoring to detect unusual SMB traffic patterns and NetNTLM hash collection attempts. Browser security policies should be configured to restrict local file access from remote content, and users should be educated about the risks of saving pages from untrusted sources. Additionally, organizations should consider implementing network segmentation and SMB hardening measures to reduce the impact of credential harvesting attacks. The vulnerability demonstrates the importance of proper input validation in web browsers and highlights the need for comprehensive security testing of download and file handling mechanisms in client-side applications.