CVE-2018-6121 in Chrome
Summary
by MITRE
Insufficient validation of input in Blink in Google Chrome prior to 66.0.3359.170 allowed a remote attacker to perform privilege escalation via a crafted HTML page.
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Analysis
by VulDB Data Team • 07/18/2024
The vulnerability identified as CVE-2018-6121 represents a critical security flaw within the Blink rendering engine of Google Chrome browsers. This issue stems from inadequate input validation mechanisms that permit malicious actors to exploit the browser's privilege escalation capabilities through carefully crafted HTML content. The vulnerability affects Chrome versions prior to 66.0.3359.170, making it a significant concern for users running outdated browser versions. The flaw specifically targets the way Blink processes user-supplied data, creating a pathway for remote code execution with elevated privileges. This type of vulnerability falls under the category of privilege escalation attacks where an attacker can leverage a web-based payload to gain higher system permissions than initially granted. The impact extends beyond simple browser compromise as it can potentially lead to full system control when combined with other exploitation techniques.
The technical root cause of this vulnerability lies in the insufficient sanitization and validation of HTML input parameters within the Blink engine's processing pipeline. When Chrome encounters malicious HTML content, the inadequate validation allows crafted elements to bypass security checks that should normally prevent privilege escalation. This flaw operates at the intersection of web browser security and operating system privilege management, where the rendering engine fails to properly isolate user-supplied content from system-level operations. The vulnerability's exploitation requires a remote attacker to deliver a malicious HTML page that triggers the flawed input validation logic, typically through JavaScript or other web technologies that interact with browser internals. Such attacks often leverage the browser's trust model where legitimate web content is processed with elevated privileges, creating a window for malicious manipulation. This vulnerability aligns with CWE-20, which addresses improper input validation, and represents a classic example of how insufficient sanitization can lead to privilege escalation in web browsers.
The operational impact of CVE-2018-6121 extends far beyond individual user compromise, potentially affecting entire enterprise environments where outdated browser versions remain in use. Organizations running legacy Chrome installations face significant risk of unauthorized system access, data exfiltration, and persistent threats that can establish footholds for broader network infiltration. Attackers can leverage this vulnerability to execute arbitrary code with system-level privileges, potentially leading to complete system compromise without requiring user interaction beyond visiting a malicious website. The remote nature of the attack means that exploitation can occur without physical access to the target system, making it particularly dangerous in corporate environments. This vulnerability enables threat actors to bypass traditional security controls that rely on browser sandboxing, as the privilege escalation allows code execution outside normal browser boundaries. The attack vector through crafted HTML pages means that even users visiting legitimate websites could be compromised if those sites have been compromised or are part of a supply chain attack. The vulnerability's presence in the rendering engine makes it particularly challenging to defend against as it operates at the core of browser functionality.
Mitigation strategies for CVE-2018-6121 primarily focus on immediate browser updates to versions 66.0.3359.170 and later, which contain the necessary patches to address the input validation deficiencies. Organizations should implement comprehensive patch management programs that prioritize browser updates, particularly for critical vulnerabilities like this one. Network administrators should consider implementing additional security layers including web application firewalls and content filtering solutions that can detect and block malicious HTML content. Browser hardening measures such as disabling unnecessary JavaScript features and restricting access to system resources can provide additional defense in depth. Security teams should monitor for indicators of compromise related to this vulnerability, including unusual network traffic patterns and system behavior that might indicate exploitation attempts. Regular security assessments of browser configurations and user access controls help identify potential exposure vectors. The vulnerability's classification under ATT&CK technique T1059.001 for command and scripting interpreter and T1068 for exploit for privilege escalation highlights the need for comprehensive endpoint protection measures. Organizations should also consider implementing user education programs to recognize suspicious web content and avoid visiting untrusted websites that could host malicious payloads. Regular vulnerability scanning and penetration testing can help identify systems running vulnerable browser versions and ensure timely remediation. The remediation process should include verification that the update has been properly applied and that the patched version is actively running on all affected systems.