CVE-2020-6526 in Chrome
Summary
by MITRE
Inappropriate implementation in iframe sandbox in Google Chrome prior to 84.0.4147.89 allowed a remote attacker to bypass navigation restrictions via a crafted HTML page.
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Analysis
by VulDB Data Team • 05/05/2025
The vulnerability identified as CVE-2020-6526 represents a critical security flaw in Google Chrome's implementation of iframe sandboxing mechanisms. This issue affects Chrome versions prior to 84.0.4147.89 and demonstrates a failure in the browser's security model that could potentially allow attackers to circumvent intended navigation restrictions. The flaw resides in how Chrome handles sandboxed iframes, specifically in the validation and enforcement of navigation boundaries that should normally prevent embedded content from accessing or redirecting to external resources. Such a vulnerability undermines the fundamental security principle that sandboxed content should be isolated from the parent browsing context and other potentially sensitive resources.
The technical implementation flaw involves the improper handling of navigation events within sandboxed iframe contexts. When a webpage contains an iframe with sandbox attributes, the browser should enforce strict restrictions on what that iframe can do, including preventing navigation to external domains, loading scripts from different origins, and accessing certain browser APIs. However, in this case, Chrome's sandbox implementation contained a logic error that allowed crafted HTML content to bypass these restrictions through specific navigation sequences. The vulnerability specifically targets the iframe sandboxing feature that is designed to contain potentially malicious or untrusted content within defined boundaries, preventing it from affecting the parent page or accessing sensitive information.
The operational impact of this vulnerability extends beyond simple navigation bypass, as it represents a potential vector for more sophisticated attacks. Attackers could craft malicious HTML pages that exploit this flaw to escape sandbox boundaries and gain access to resources that should normally be restricted. This could enable information disclosure, cross-site scripting attacks, or even privilege escalation within the browser context. The vulnerability's remote exploitation capability means that simply visiting a malicious webpage could result in unauthorized access or data compromise without requiring any user interaction beyond navigation. This aligns with ATT&CK technique T1059.001 for command and scripting interpreter, as attackers could leverage the bypassed sandbox to execute malicious code within the browser environment.
The flaw's implications are particularly concerning given Chrome's widespread usage and the extensive permissions that browsing contexts typically possess. When sandbox restrictions are bypassed, attackers gain access to sensitive browser functionality and could potentially access cookies, local storage, or other session data that should remain isolated. This vulnerability demonstrates a failure in the principle of least privilege that should govern how embedded content interacts with the host browsing environment. Security researchers categorize this type of issue under CWE-284, which addresses improper access control, specifically in the context of sandboxed environments where access control mechanisms are supposed to be enforced.
Mitigation strategies for CVE-2020-6526 primarily involve updating to Chrome version 84.0.4147.89 or later, which contains the necessary patches to correct the sandbox implementation. Organizations should also consider implementing additional security measures such as content security policies that further restrict iframe behavior, regular browser updates as part of security maintenance procedures, and monitoring for suspicious navigation patterns in web applications. The vulnerability highlights the importance of robust sandbox implementation and the need for continuous security auditing of browser security features. Security teams should also be aware that this type of sandbox bypass could potentially be combined with other vulnerabilities to create more sophisticated attack chains, making comprehensive browser security assessment crucial for maintaining secure web environments.