CVE-2023-4045 in Firefox
Summary
by MITRE • 08/01/2023
Offscreen Canvas did not properly track cross-origin tainting, which could have been used to access image data from another site in violation of same-origin policy. This vulnerability affects Firefox < 116, Firefox ESR < 102.14, and Firefox ESR < 115.1.
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Analysis
by VulDB Data Team • 06/20/2025
The vulnerability identified as CVE-2023-4045 resides within the Offscreen Canvas implementation of Mozilla Firefox browsers, specifically affecting versions prior to 116 and certain ESR releases. This flaw represents a critical breach in the browser's security model that undermines the fundamental same-origin policy enforcement mechanism. The issue manifests when the Offscreen Canvas API fails to properly track cross-origin tainting status, creating a pathway for malicious actors to bypass security boundaries that should prevent access to image data from different origins. The vulnerability directly impacts the integrity of web application security by allowing unauthorized data extraction across domain boundaries.
The technical root cause of this vulnerability lies in the improper handling of cross-origin resource tracking within the Offscreen Canvas API implementation. When images are loaded from different origins, the browser should enforce strict tainting rules that prevent access to pixel data or other sensitive information from cross-origin sources. However, the flaw allows for scenarios where tainted resources can be accessed through the Offscreen Canvas context, effectively circumventing the same-origin policy that forms the cornerstone of web security. This misimplementation creates a vector for information disclosure attacks where attackers can extract image data from external domains without proper authorization. The vulnerability operates at the intersection of web standards and browser security implementation, where the Offscreen Canvas API's interaction with cross-origin resources fails to maintain proper security boundaries.
The operational impact of CVE-2023-4045 extends beyond simple information disclosure, as it represents a significant weakening of browser security that could enable more sophisticated attacks. Attackers could potentially use this vulnerability to extract sensitive image data from third-party services, including but not limited to user profile pictures, authentication tokens embedded in images, or other cross-origin resources that should remain protected. The vulnerability affects not just regular browser users but also enterprise environments where Firefox is deployed as the primary browser, potentially exposing organizations to data exfiltration attacks. Given that the affected versions include ESR releases, enterprise deployments that rely on long-term support versions are particularly at risk, as these releases typically receive extended support periods and are considered stable for business use.
Organizations should prioritize immediate remediation by updating to Firefox 116 or the appropriate ESR versions that contain the fix for this vulnerability. Security teams should also implement monitoring for potential exploitation attempts and consider temporary mitigations such as disabling Offscreen Canvas functionality where possible. The vulnerability aligns with CWE-200 (Information Exposure) and represents a specific implementation flaw in the browser's security model that violates the principle of least privilege. From an ATT&CK framework perspective, this vulnerability could be leveraged as part of a broader attack chain under techniques such as T1071.001 (Application Layer Protocol: Web Protocols) and T1566 (Phishing) where attackers might use the information disclosure to gather intelligence for further attacks. The remediation process should include thorough testing of browser functionality to ensure that legitimate use cases of Offscreen Canvas are not disrupted while addressing the security gap.