CVE-2016-2845 in Chrome
Summary
by MITRE
The Content Security Policy (CSP) implementation in Blink, as used in Google Chrome before 49.0.2623.75, does not ignore a URL's path component in the case of a ServiceWorker fetch, which allows remote attackers to obtain sensitive information about visited web pages by reading CSP violation reports, related to FrameFetchContext.cpp and ResourceFetcher.cpp.
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Analysis
by VulDB Data Team • 07/09/2022
The vulnerability described in CVE-2016-2845 represents a critical information disclosure flaw within the Content Security Policy implementation of Google Chrome's Blink rendering engine. This issue specifically affects versions prior to 49.0.2623.75 and stems from an improper handling of URL path components during ServiceWorker fetch operations. The flaw exists in the FrameFetchContext.cpp and ResourceFetcher.cpp components of the browser's architecture, creating a pathway for remote attackers to exploit the CSP mechanism for unauthorized data collection. The vulnerability exploits the fundamental principle that CSP should prevent unauthorized resource loading while maintaining strict boundaries between different origins and contexts.
The technical implementation flaw occurs when ServiceWorker fetch requests are processed within the Blink engine, where the Content Security Policy logic fails to properly isolate the path component of URLs during violation report generation. This oversight allows attackers to craft malicious requests that can cause the browser to include sensitive path information in CSP violation reports, which are then transmitted to the attacker-controlled server. The vulnerability specifically targets the way the browser handles cross-origin resource requests and the subsequent reporting mechanism that should normally prevent such information leakage. This improper path handling creates a scenario where the CSP implementation inadvertently exposes visited page information, effectively bypassing the security controls designed to protect user privacy.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables sophisticated reconnaissance attacks that can reveal user browsing patterns and visited web resources. Attackers can leverage this flaw to construct targeted campaigns that monitor user activity across different domains, potentially mapping out user interests and online behavior without explicit user consent. The vulnerability is particularly dangerous in environments where users access sensitive information or perform confidential activities, as it could expose the nature of their online activities through the CSP violation reporting mechanism. This creates a vector for surveillance and tracking that undermines the privacy guarantees that CSP is designed to provide, potentially affecting users in high-risk scenarios such as journalists, activists, or individuals in sensitive professional roles.
The vulnerability aligns with CWE-200, which describes improper information exposure, and represents a specific instance of how security controls can be circumvented through implementation flaws in complex software systems. From an ATT&CK framework perspective, this vulnerability maps to techniques involving information gathering and reconnaissance, specifically T1082 for system information discovery and T1566 for spearphishing with a malicious attachment or link. The flaw demonstrates how seemingly minor implementation details in security-critical components can create significant attack surface, emphasizing the importance of thorough security testing and code review processes. Organizations should prioritize updating affected systems to versions that properly address the path component handling in CSP implementations, while also implementing network monitoring to detect potential exploitation attempts through CSP violation reports. The incident underscores the need for comprehensive security testing of browser components and the importance of maintaining up-to-date software to protect against known vulnerabilities that could compromise user privacy and security.