CVE-2020-6400 in Chrome
Summary
by MITRE
Inappropriate implementation in CORS in Google Chrome prior to 80.0.3987.87 allowed a remote attacker to leak cross-origin data via a crafted HTML page.
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Analysis
by VulDB Data Team • 05/10/2025
The vulnerability identified as CVE-2020-6400 represents a critical flaw in Google Chrome's implementation of Cross-Origin Resource Sharing (CORS) mechanisms. This weakness existed in Chrome versions prior to 80.0.3987.87 and enabled remote attackers to exploit improper handling of cross-origin requests. The issue stems from Chrome's inadequate enforcement of CORS policies when processing specially crafted HTML pages, creating a pathway for unauthorized data leakage between different origins. The vulnerability specifically targets the browser's security model that should prevent websites from accessing resources hosted on different domains without proper authorization. Attackers could leverage this flaw by constructing malicious web pages that trigger cross-origin requests in ways that bypass Chrome's security controls, potentially allowing them to access sensitive data from other origins that should be restricted.
The technical implementation flaw manifests in how Chrome processes CORS preflight requests and response handling when encountering maliciously crafted HTML content. The vulnerability exploits a gap in the browser's validation logic where it fails to properly verify the origin of requests during cross-origin operations. This allows attackers to craft HTML pages that manipulate the browser's CORS decision-making process, potentially enabling data exfiltration from legitimate websites that have proper CORS configurations. The flaw operates at the application layer of the network stack, specifically within Chrome's HTTP request processing pipeline where CORS headers are evaluated and acted upon. According to CWE-346, this vulnerability falls under improper verification of critical assumptions, as Chrome incorrectly assumes that certain CORS configurations are sufficient to prevent unauthorized access patterns. The issue represents a failure in the browser's security architecture to properly isolate cross-origin resources, creating an attack surface that violates fundamental web security principles.
The operational impact of this vulnerability extends beyond simple data leakage, potentially enabling sophisticated attacks that could compromise user privacy and web application security. An attacker could use this vulnerability to access sensitive information from authenticated sessions, potentially leading to account takeovers or data breaches. The remote nature of the attack means that users could be compromised simply by visiting malicious websites or clicking on compromised links, without requiring any special privileges or local access. This type of vulnerability directly impacts the integrity of the browser's security model and could be exploited in conjunction with other techniques to create more complex attack vectors. The vulnerability affects not only individual users but also organizations that rely on Chrome for web browsing, as it undermines the trust model that web applications depend upon for secure cross-origin communication. The attack could be particularly dangerous in enterprise environments where users access sensitive corporate data through Chrome browsers, as it could enable unauthorized access to internal resources that should be protected by CORS policies.
Mitigation strategies for CVE-2020-6400 focus primarily on updating Chrome to versions 80.0.3987.87 or later, where Google has implemented proper CORS validation mechanisms. Organizations should also implement additional security measures including network monitoring to detect unusual cross-origin requests, content security policies to restrict resource loading from untrusted origins, and regular security assessments to identify potential exploitation attempts. Browser security configurations should be reviewed to ensure that CORS policies are properly enforced at both the application and network levels. The vulnerability highlights the importance of maintaining up-to-date browser software and implementing defense-in-depth strategies that protect against various attack vectors. Security teams should also consider implementing web application firewalls that can detect and block suspicious cross-origin request patterns. According to ATT&CK framework, this vulnerability aligns with techniques related to privilege escalation and credential access through web-based attacks, emphasizing the need for comprehensive browser security monitoring and response procedures. Organizations should also conduct regular security awareness training to help users recognize potentially malicious web content that could exploit such vulnerabilities.