CVE-2026-85094 in Canva
Summary
by MITRE • 09/04/2026
The Canva Android App before 2.376.0 did not restrict the headers returned to an external origin running in a privileged WebView. A threat actor with control of the WebView could access a user’s session.
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Analysis
by VulDB Data Team • 09/04/2026
The vulnerability identified in versions of the Canva Android application prior to release 2.376.0 stems from an improper configuration of cross-origin resource sharing policies within the application's embedded web views. Specifically, the application failed to restrict or filter HTTP headers returned by external origins when those requests were processed through a privileged WebView component. In mobile application architecture, WebViews are often granted elevated permissions that allow them to access local storage, cookies, and session tokens with greater ease than standard browser contexts. When an external origin is loaded within such a context without strict header restrictions, the boundary between the trusted application environment and untrusted web content becomes porous. This architectural flaw allows data intended for internal use or restricted by security policies to be exposed to scripts running in the WebView if those scripts can manipulate or inspect the response headers from cross-origin requests.
The technical core of this issue lies in the lack of validation on HTTP response headers originating from third-party domains loaded within the privileged context. Typically, browsers enforce strict same-origin policies that prevent a script hosted on one domain from accessing resources or metadata belonging to another unless explicitly permitted via CORS mechanisms like Access-Control-Allow-Origin. However, when an Android WebView is configured with specific flags such as allowFileAccess or has access to application-specific cookies and session storage, it may inadvertently expose sensitive header information if the underlying network stack does not properly isolate these responses from malicious scripts. A threat actor who gains control over the content loaded in this WebView, either through a compromised third-party script injection or by directing the user to a malicious URL hosted within the app's web view, can exploit this exposure. By analyzing the returned headers, an attacker can extract session identifiers, authentication tokens, or other sensitive metadata that are not adequately sanitized before being passed back to the JavaScript execution context.
The operational impact of this vulnerability is severe, primarily centering on account takeover and unauthorized access to user data. Since Canva handles creative assets, personal projects, and potentially corporate intellectual property for its users, the compromise of a session token allows an attacker to impersonate the legitimate user without needing their password or multi-factor authentication credentials. This bypasses standard security controls that rely on credential secrecy. The attacker can perform actions as the victim, such as modifying designs, accessing private teams, exporting sensitive documents, or using up subscription limits. Furthermore, because this occurs within a mobile application context where users may have granted broad permissions to the app for convenience, the attack surface is expanded beyond traditional web-based attacks. This represents a significant risk to user privacy and data integrity, potentially leading to long-term reputational damage for both the end-user and the service provider if large-scale breaches occur due to this single point of failure in header handling logic.
To mitigate this vulnerability, it is critical to enforce strict Content Security Policy (CSP) directives within all WebView instances used by the application. Developers should ensure that CSP headers explicitly restrict sources from which scripts can be loaded and prevent inline script execution where possible. Additionally, implementing robust CORS policies on any backend services interacting with these WebViews ensures that only whitelisted origins are permitted to receive sensitive data. The response headers must be carefully audited to remove or sanitize any information that could aid in session hijacking, such as setting appropriate Cache-Control and Pragma directives to prevent caching of sensitive responses. Upgrading the application to version 2.376.0 or later resolves this issue by implementing stricter header filtering mechanisms within the WebView environment. Security teams should also consider adopting defense-in-depth strategies, including using separate WebView instances for untrusted content with restricted permissions, thereby isolating potentially malicious web pages from privileged session data.
This vulnerability aligns with CWE-201, which describes Information Exposure Through Sent Data, as sensitive information was inadvertently exposed via HTTP headers to an unauthorized actor. It also maps to the MITRE ATT&CK technique T1539, specifically under Steal Web Session Cookie, where attackers target session tokens transmitted in cookies or headers within web applications and APIs. The exploitation vector relates to improper input validation of cross-origin requests, highlighting the importance of treating all external content loaded within privileged contexts as untrusted. By addressing these configuration flaws and adhering to secure coding standards for mobile WebView implementations, developers can prevent similar exposures that compromise user session integrity across various platforms.