CVE-2021-32683 in wire-webapp
Summary
by MITRE • 06/16/2021
wire-webapp is the web version of Wire, an open-source messenger. A cross-site scripting vulnerability exists in wire-webapp prior to version 2021-06-01-production.0. If a user is instructed to open an image in a new tab (right click -> open in new tab, or copy the URL and paste it in the URL bar), an the image payload is executed on the domain hosting the app (app.wire.com). In particular, if an image contains malicious code in addition to the actual picture, this code is executed on app.wire.com. This allows the attacker to fully control the user account. The vulnerability was patched in version 2021-06-01-production.0. As a workaround, users should not try to open image URLs.
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Analysis
by VulDB Data Team • 06/18/2021
The vulnerability CVE-2021-32683 represents a critical cross-site scripting flaw in the wire-webapp component of the Wire messaging platform, which operates as an open-source communication solution. This vulnerability specifically affects versions prior to the 2021-06-01-production.0 release and demonstrates a significant security weakness in how the application handles image payloads when users attempt to view images in new browser tabs. The flaw exploits user interaction patterns where individuals might right-click on images to open them in new tabs or manually copy and paste image URLs into their browser address bars, creating an attack surface that adversaries can leverage for unauthorized access.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding within the wire-webapp's image handling mechanisms. When users navigate to image URLs through the specified interaction patterns, the application fails to properly sanitize or escape the image content before rendering it within the context of the app domain. This allows malicious code embedded within image files to execute in the security context of app.wire.com, effectively granting attackers the ability to manipulate the application's behavior and user session. The vulnerability operates at the intersection of several security principles, including proper content sanitization, context-aware output encoding, and secure handling of user-provided data.
The operational impact of CVE-2021-32683 is severe and potentially catastrophic for affected users, as successful exploitation enables full account compromise. Attackers who successfully leverage this vulnerability can gain complete control over user sessions, allowing them to read, modify, or delete messages, access contacts, and potentially escalate privileges within the application. This represents a direct violation of the principle of least privilege and demonstrates how a single flaw in image handling can create a complete session hijacking vector. The vulnerability's exploitation requires minimal user interaction beyond normal browsing behavior, making it particularly dangerous in real-world scenarios where users might unknowingly trigger the attack.
From a cybersecurity framework perspective, this vulnerability aligns with CWE-79 (Cross-site Scripting) and maps to ATT&CK techniques including T1059.007 (Command and Scripting Interpreter: JavaScript) and T1566.001 (Phishing: Spearphishing Attachment). The flaw demonstrates inadequate defense-in-depth measures, particularly in the application's content security policy implementation and input validation mechanisms. Organizations relying on Wire for secure communications would face significant risk exposure, as the vulnerability could enable attackers to access sensitive business communications, personal data, and potentially facilitate broader network infiltration. The patch released in version 2021-06-01-production.0 addressed the core issue through enhanced input sanitization and improved context-aware output encoding for image content.
The recommended mitigation strategy involves immediate deployment of the patched version and implementation of user education regarding the dangers of opening suspicious image URLs in new tabs. Additionally, organizations should consider implementing enhanced content security policies, regular security scanning of image content, and monitoring for anomalous user behavior patterns that might indicate exploitation attempts. The vulnerability serves as a reminder of the critical importance of proper input validation and output encoding in web applications, particularly when handling user-generated content that may be executed in trusted application contexts.