CVE-2019-9817 in Firefox
Summary
by MITRE
Images from a different domain can be read using a canvas object in some circumstances. This could be used to steal image data from a different site in violation of same-origin policy. This vulnerability affects Thunderbird < 60.7, Firefox < 67, and Firefox ESR < 60.7.
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Analysis
by VulDB Data Team • 06/05/2024
This vulnerability represents a critical security flaw in web browser implementations that violates fundamental web security principles. The issue stems from improper handling of cross-origin resource sharing within canvas objects, specifically allowing malicious code to bypass the same-origin policy that protects users from unauthorized data access between different domains. The vulnerability exists in the rendering engine's interpretation of image data when canvas operations are performed across domain boundaries, creating a pathway for unauthorized data exfiltration.
The technical exploitation occurs when a malicious website attempts to read image data from a different origin using canvas operations. When an image from another domain is drawn onto a canvas element, the browser should normally prevent access to the underlying pixel data due to security restrictions. However, this vulnerability allows attackers to circumvent these protections, enabling them to extract image content that should be restricted by the same-origin policy. The flaw specifically affects the way browsers handle image data retrieval and canvas manipulation when dealing with cross-domain resources, creating a covert channel for data theft.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables sophisticated attacks that can harvest sensitive visual data from other websites. Attackers can leverage this weakness to steal user avatars, security images, or any visual content that might contain sensitive information, potentially leading to identity theft, social engineering attacks, or further exploitation. The vulnerability affects major browser implementations including Firefox and Thunderbird, making it a widespread concern across multiple platforms and applications that rely on web technologies for user interfaces and data display.
Security mitigations for this vulnerability involve implementing proper cross-origin resource sharing controls within browser rendering engines, ensuring that canvas operations respect origin boundaries, and applying patches that address the specific implementation flaw in image handling. The affected versions require immediate updates to prevent exploitation, as the vulnerability can be leveraged by attackers to perform unauthorized data access operations. Organizations should prioritize patch management for these browser versions, while developers should implement additional security measures such as content security policies and proper origin validation when working with canvas-based operations. This vulnerability aligns with CWE-200 (Information Exposure) and represents a violation of the ATT&CK technique T1071.004 (Application Layer Protocol: DNS) in scenarios where attackers might use similar cross-origin techniques to access restricted resources. The fix typically involves strengthening the same-origin policy enforcement within canvas operations and ensuring that image data access is properly restricted based on domain boundaries and user permissions.