CVE-2016-1954 in Firefox
Summary
by MITRE
The nsCSPContext::SendReports function in dom/security/nsCSPContext.cpp in Mozilla Firefox before 45.0 and Firefox ESR 38.x before 38.7 does not prevent use of a non-HTTP report-uri for a Content Security Policy (CSP) violation report, which allows remote attackers to cause a denial of service (data overwrite) or possibly gain privileges by specifying a URL of a local file.
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Analysis
by VulDB Data Team • 10/23/2024
The vulnerability identified as CVE-2016-1954 resides within the Content Security Policy implementation of Mozilla Firefox, specifically in the nsCSPContext::SendReports function located in dom/security/nsCSPContext.cpp. This flaw represents a critical security oversight that affects Firefox versions prior to 45.0 and Firefox ESR 38.x versions prior to 38.7. The vulnerability stems from insufficient validation of report-uri parameters within CSP directives, creating a pathway for malicious exploitation through improper handling of URI schemes during security violation reporting.
The technical flaw manifests when the browser processes Content Security Policy violation reports and fails to properly validate the URI scheme of the report destination. This allows attackers to specify report-uri values that reference local file systems rather than standard HTTP endpoints. The vulnerability is categorized under CWE-20, "Improper Input Validation," and specifically relates to improper validation of URI schemes in security contexts. When a malicious CSP policy is enforced with a report-uri pointing to a local file system location, the browser attempts to write violation reports to these local destinations, potentially overwriting critical system files or creating unauthorized data access points.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially enable privilege escalation attacks. Remote attackers can leverage this flaw to cause data overwrite operations on the local file system, which may result in system instability, data corruption, or unauthorized modification of critical application files. The vulnerability enables attackers to manipulate the browser's reporting mechanism to target local resources, potentially allowing for persistent access or privilege elevation depending on the target system's configuration and the specific local file paths chosen. This represents a significant concern for enterprise environments where browser-based attacks can compromise user systems and potentially spread laterally within networks.
Security practitioners should implement immediate mitigations including updating to Firefox versions 45.0 or later for regular releases, and Firefox ESR 38.7 or later for extended support releases. Organizations should also consider implementing network-level restrictions to prevent access to local file systems from browser processes and monitor for unusual file system access patterns in security logs. The vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter, specifically through the manipulation of browser security features to achieve unauthorized system access. Additionally, this issue demonstrates the importance of proper URI validation in security contexts and the potential for seemingly benign security features to become attack vectors when input validation is insufficient. Organizations should conduct thorough security assessments of their browser deployment configurations to ensure CSP policies are properly enforced and that report-uri values are validated against acceptable URI schemes to prevent similar vulnerabilities from being exploited.