CVE-2014-8638 in Firefox
Summary
by MITRE
The navigator.sendBeacon implementation in Mozilla Firefox before 35.0, Firefox ESR 31.x before 31.4, Thunderbird before 31.4, and SeaMonkey before 2.32 omits the CORS Origin header, which allows remote attackers to bypass intended CORS access-control checks and conduct cross-site request forgery (CSRF) attacks via a crafted web site.
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Analysis
by VulDB Data Team • 03/02/2022
The vulnerability described in CVE-2014-8638 represents a critical security flaw in the navigator.sendBeacon API implementation within Mozilla Firefox and related browser products. This issue affects versions prior to Firefox 35.0, Firefox ESR 31.x before 31.4, Thunderbird before 31.4, and SeaMonkey before 2.32, creating a significant bypass of web application security mechanisms that rely on cross-origin resource sharing controls. The flaw specifically impacts the navigator.sendBeacon API which is designed to allow web applications to send analytics data and other information to servers in a way that persists across page navigation and browser shutdown events.
The technical root cause of this vulnerability lies in the improper handling of CORS (Cross-Origin Resource Sharing) headers within the sendBeacon implementation. When web applications use the sendBeacon API to transmit data to remote servers, the browser should include the Origin header as part of the CORS protocol to establish the origin of the request. However, Firefox versions affected by this vulnerability failed to include the CORS Origin header in these requests, effectively removing the origin validation that CORS security mechanisms depend upon. This omission allows malicious websites to craft requests that appear to originate from legitimate domains, thereby bypassing the intended access controls that should prevent unauthorized cross-origin operations.
The operational impact of this vulnerability is severe as it enables remote attackers to conduct cross-site request forgery attacks with significant implications for web application security. Attackers can leverage this flaw to manipulate web applications that rely on CORS for access control by crafting malicious websites that send beacon requests to target applications without proper origin validation. This capability undermines the fundamental security model of web applications and could potentially allow unauthorized actions to be performed on behalf of users, particularly in scenarios where applications use CORS policies to restrict access to sensitive operations or data. The vulnerability essentially creates a pathway for attackers to circumvent the browser's security model and perform unauthorized requests that would normally be blocked by CORS controls.
This vulnerability maps directly to CWE-346, which addresses "Origin Validation Error" in web applications, and aligns with ATT&CK technique T1566.001 for "Phishing: Spearphishing Attachment" and T1566.002 for "Phishing: Spearphishing Link" as attackers can exploit this weakness to deliver malicious payloads through crafted web content. The security implications extend beyond simple data exfiltration to include potential account takeovers, unauthorized transactions, and privilege escalation attacks when combined with other exploitation techniques. Organizations relying on Firefox for web browsing and application development should consider this vulnerability as a critical threat to their security posture, particularly in environments where CORS policies are used as primary access control mechanisms for web services and APIs.
The recommended mitigation strategy involves immediate upgrading to patched versions of Firefox, Thunderbird, and SeaMonkey where the CORS Origin header is properly implemented in the navigator.sendBeacon API. System administrators should also implement additional monitoring for anomalous beacon requests and consider implementing web application firewalls or security policies that can detect and block suspicious cross-origin requests. Organizations should conduct thorough security assessments of their web applications to identify potential reliance on CORS for access control and ensure that alternative security measures are implemented to protect against this type of attack vector. The vulnerability underscores the importance of proper implementation of security protocols in browser APIs and highlights the critical need for continuous security auditing of browser components that handle cross-origin communications.