CVE-2018-6066 in Chrome
Summary
by MITRE
Lack of CORS checking by ResourceFetcher/ResourceLoader in Blink in Google Chrome prior to 65.0.3325.146 allowed a remote attacker to leak cross-origin data via a crafted HTML page.
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Analysis
by VulDB Data Team • 06/06/2023
The vulnerability identified as CVE-2018-6066 represents a critical security flaw in the Blink rendering engine used by Google Chrome browsers. This issue specifically affects versions prior to 65.0.3325.146 and stems from insufficient Cross-Origin Resource Sharing (CORS) validation mechanisms within the ResourceFetcher and ResourceLoader components. The flaw enables malicious actors to exploit the browser's resource loading behavior to access sensitive cross-origin data that should typically be restricted by web security policies. The vulnerability operates at the core level of browser security architecture where origin-based access controls should prevent unauthorized data leakage between different web domains.
The technical implementation of this vulnerability exploits the way Blink handles resource loading and validation processes. When a browser encounters resources from different origins, it should enforce strict CORS policies to ensure that cross-origin requests are properly authorized before any data transfer occurs. However, the ResourceFetcher and ResourceLoader components in affected Chrome versions failed to adequately validate these cross-origin requests, creating a pathway for attackers to craft malicious HTML pages that could bypass normal security boundaries. This flaw essentially allows a remote attacker to construct web pages that can trigger resource requests to other domains and potentially capture response data that should remain protected. The vulnerability manifests through the browser's internal resource management systems rather than through traditional attack vectors, making it particularly insidious as it operates within the core browser functionality.
The operational impact of this vulnerability extends beyond simple data leakage to potentially enable more sophisticated attacks including credential theft, session hijacking, and sensitive information exposure across different web applications. Attackers could leverage this flaw to access data from authenticated sessions, private APIs, or protected resources that should normally be inaccessible due to CORS restrictions. The implications are particularly severe in enterprise environments where users may browse multiple applications that rely on proper cross-origin security boundaries. This vulnerability directly violates the fundamental security principle of origin isolation that web browsers implement to protect users from cross-site scripting attacks and unauthorized data access. The flaw represents a breakdown in the browser's security model and could potentially allow attackers to escalate privileges or access sensitive data that would normally be protected by standard web security mechanisms.
Mitigation strategies for CVE-2018-6066 primarily focus on updating to patched versions of Google Chrome where the CORS validation has been properly implemented in the ResourceFetcher and ResourceLoader components. Organizations should prioritize immediate deployment of Chrome version 65.0.3325.146 or later to address this vulnerability. Additionally, network administrators should implement additional security layers including content security policies that further restrict cross-origin resource access. The vulnerability aligns with CWE-346, which addresses "Origin Validation Error" and represents a failure in proper origin validation mechanisms. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access and data extraction through browser-based attacks. Organizations should also consider implementing web application firewalls and monitoring for unusual cross-origin requests that might indicate exploitation attempts. The fix implemented by Google involved strengthening the CORS validation checks within the browser's core resource loading architecture to ensure proper origin verification before any cross-origin data transfer occurs.