CVE-2016-1955 in Firefox
Summary
by MITRE
Mozilla Firefox before 45.0 allows remote attackers to bypass the Same Origin Policy and obtain sensitive information by reading a Content Security Policy (CSP) violation report that contains path information associated with an IFRAME element.
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Analysis
by VulDB Data Team • 07/09/2022
The vulnerability identified as CVE-2016-1955 represents a critical security flaw in Mozilla Firefox versions prior to 45.0 that undermines the fundamental Same Origin Policy mechanism. This policy serves as a cornerstone of web security by preventing malicious websites from accessing resources from different origins, thereby protecting users from cross-site scripting attacks and data exfiltration attempts. The flaw specifically exploits how Firefox handles Content Security Policy violation reports, creating a pathway for attackers to gather sensitive information about file paths and system structures through seemingly innocuous CSP violation messages.
The technical implementation of this vulnerability stems from Firefox's improper handling of CSP violation reports that contain path information associated with iframe elements. When a web application violates a Content Security Policy, Firefox generates a violation report that should only contain minimal information about the policy violation. However, in affected versions, these reports inadvertently exposed path information that could reveal sensitive details about the target system's directory structure. Attackers could craft malicious web pages that trigger CSP violations in targeted browsers, then capture and analyze the violation reports to extract path information that might reveal system configurations, application structures, or other sensitive data.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables attackers to perform reconnaissance activities that would normally be blocked by proper security controls. An attacker could leverage this flaw to map out web application structures, identify system paths, and gather intelligence that could be used for more sophisticated attacks. The vulnerability is particularly dangerous because it operates at the browser level, meaning that even if the target website implements proper security measures, the browser itself becomes a vector for information leakage. This creates a scenario where legitimate security controls are bypassed through a flaw in the browser's security model, potentially exposing users to further exploitation.
This vulnerability aligns with CWE-200, which describes improper exposure of sensitive information, and maps to ATT&CK technique T1082, which involves system information discovery. The flaw demonstrates how browser security mechanisms can be circumvented through improper handling of security reports and logging, creating a vector for reconnaissance that bypasses traditional web application security controls. Organizations should prioritize immediate patching of affected Firefox installations to mitigate this risk, as the vulnerability exists in the browser's core security architecture rather than in specific web applications. Additionally, security monitoring should include detection of unusual CSP violation report patterns that might indicate exploitation attempts, and network administrators should consider implementing additional filtering measures to prevent unauthorized access to potentially sensitive information that could be exposed through such mechanisms.