CVE-2018-6052 in Chrome
Summary
by MITRE
Lack of support for a non standard no-referrer policy value in Blink in Google Chrome prior to 64.0.3282.119 allowed a remote attacker to obtain referrer details from a web page that had thought it had opted out of sending referrer data.
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Analysis
by VulDB Data Team • 02/03/2023
The vulnerability identified as CVE-2018-6052 represents a critical flaw in Google Chrome's Blink rendering engine that affected versions prior to 64.0.3282.119. This issue stems from the browser's inadequate handling of non-standard referrer policy values, creating a security gap that could be exploited by remote attackers to bypass intended privacy protections. The vulnerability specifically targets the referrer policy implementation within the browser's core rendering components, where the system failed to properly validate or reject unconventional policy specifications that should have prevented referrer data transmission.
The technical flaw manifests when web pages implement referrer policies with non-standard values that deviate from the established web standards defined by the W3C. In normal operation, browsers should honor referrer policies that explicitly opt out of sending referrer information, but Chrome's Blink engine demonstrated inconsistent behavior when encountering these non-standard values. This inconsistency allowed attackers to craft web pages or manipulate existing pages in such a way that referrer data would be transmitted despite the page's apparent intention to disable such tracking. The vulnerability essentially created a bypass mechanism that undermined the privacy controls that web developers and users expected to be in place.
The operational impact of this vulnerability extends beyond simple privacy concerns to encompass potential data leakage and tracking capabilities that could be exploited by malicious actors. When a user navigates from a page that has implemented a referrer policy to another page, normally the referrer information should not be transmitted if the policy explicitly opts out. However, this flaw allowed attackers to extract referrer details from pages that had implemented what they believed to be effective privacy controls. The implications are significant for users who rely on referrer policies to prevent tracking by third-party services, as the vulnerability could enable persistent tracking across different domains and applications, undermining user privacy expectations and potentially exposing sensitive navigation patterns.
This vulnerability aligns with CWE-200, which addresses "Information Exposure," and represents a failure in proper input validation and policy enforcement within the browser's security model. From an attack perspective, this flaw maps to techniques described in the MITRE ATT&CK framework under the "Initial Access" and "Persistence" phases, where attackers could leverage this weakness to establish tracking capabilities without user knowledge. The vulnerability also intersects with the broader category of web security flaws related to HTTP headers and policy enforcement, making it particularly dangerous in environments where users expect strong privacy controls. The fact that this issue affected a widely used browser like Chrome amplifies its potential impact, as it could be exploited across millions of users who rely on the browser's security mechanisms to protect their online activities from tracking and data collection.
The mitigation strategy for CVE-2018-6052 requires immediate browser updates to version 64.0.3282.119 or later, which implements proper validation of referrer policy values and ensures consistent enforcement of privacy controls. Additionally, web developers should review their referrer policy implementations to ensure they use only standard policy values and avoid relying on potentially non-compliant browser behavior. Security administrators should monitor for signs of exploitation attempts and consider implementing additional network-level controls to detect and prevent unauthorized referrer data transmission. Organizations should also conduct regular security assessments to verify that their browser configurations properly enforce referrer policies and maintain up-to-date security patches to prevent similar vulnerabilities from being exploited.