CVE-2026-78987 in Chrome
Summary
by MITRE • 08/26/2026
Information leak in Canvas in Google Chrome prior to 152.0.7977.65 allowed a remote attacker to bypass web origin policy via a crafted HTML page. (Chromium security severity: Medium)
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Analysis
by VulDB Data Team • 08/26/2026
The vulnerability identified as an information leak within the Canvas API of Google Chrome, specifically in versions prior to 152.0.7977.65, represents a significant breach of web origin policies that enables remote attackers to exfiltrate sensitive data from cross-origin contexts. This flaw stems from insufficient isolation mechanisms when rendering graphical content via HTML5 Canvas elements, allowing scripts loaded from one domain to inadvertently access pixel data or metadata associated with resources hosted on a different domain. Under normal security models enforced by the browser's same-origin policy, such cross-domain interactions are strictly prohibited to prevent unauthorized data theft and session hijacking. However, due to this specific implementation error in the rendering engine, crafted HTML pages could exploit race conditions or improper state management within the Canvas drawing context to read back pixel values that were drawn using images loaded from external sources without proper CORS headers or explicit permission grants.
From a technical perspective, the core issue lies in how the browser handles tainted canvas data when mixed with cross-origin resources. When an image is fetched from a different origin and drawn onto a canvas element, modern browsers typically mark that canvas as tainted to prevent subsequent readback operations via methods like getImageData or toDataURL unless specific security checks are passed. In this vulnerable version of Chrome, these checks were bypassed under certain conditions, likely involving asynchronous loading sequences where the browser failed to correctly flag the canvas state before allowing script execution to query its contents. This allows an attacker hosting a malicious webpage on their own server to load images from victim sites and then extract visual information such as screenshots, user interface elements, or even sensitive text rendered within those images. The severity is classified as medium by Chromium security standards because while it does not allow direct code execution or full system compromise, it facilitates sophisticated surveillance and data scraping attacks that can lead to further exploitation chains.
The operational impact of this vulnerability extends beyond simple data leakage, affecting the integrity of web applications that rely on canvas for rendering charts, maps, games, or image processing tools. Attackers could use this technique to perform fingerprinting by extracting unique visual artifacts from user interfaces, thereby enhancing tracking capabilities across different websites without consent. Furthermore, if sensitive information such as authentication tokens displayed in images, private messages rendered graphically, or proprietary designs are exposed through canvas readback operations, the confidentiality guarantees provided by HTTPS and origin policies are effectively nullified for those specific assets. This undermines trust in web-based applications and exposes users to privacy violations that are difficult to detect using traditional security monitoring tools since the data transfer occurs locally within the browser process before being sent out via standard HTTP requests initiated by the malicious script.
Mitigation strategies primarily involve upgrading Google Chrome to version 152.0.7977.65 or later, where these origin policy enforcement mechanisms have been hardened and cross-origin resource sharing checks are strictly applied during canvas operations. For organizations unable to immediately patch all endpoints, implementing strict Content Security Policy directives can help mitigate risk by restricting the sources from which images can be loaded into canvas elements and disabling inline scripts that might attempt such exploits. Additionally, developers should ensure that any server hosting resources intended for use in cross-origin contexts properly configures CORS headers with appropriate Access-Control-Allow-Origin values to explicitly permit or deny access rather than relying solely on browser-side defaults. Regular security audits focusing on HTML5 API usage patterns can also help identify similar implementation flaws before they are exploited by threat actors leveraging automated scanning tools designed to probe canvas-related vulnerabilities in modern web browsers.