CVE-2021-45087 in Epiphany
Summary
by MITRE • 12/16/2021
XSS can occur in GNOME Web (aka Epiphany) before 40.4 and 41.x before 41.1 when View Source mode or Reader mode is used, as demonstrated by a a page title.
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Analysis
by VulDB Data Team • 12/18/2021
The vulnerability identified as CVE-2021-45087 represents a cross-site scripting flaw affecting GNOME Web browser commonly known as Epiphany. This security weakness exists in versions prior to 40.4 and 41.x before 41.1, specifically manifesting when users engage with either View Source mode or Reader mode functionality. The exploit occurs through manipulation of page titles, demonstrating how seemingly innocuous user interface elements can become attack vectors in web browsing applications.
The technical implementation of this vulnerability stems from inadequate input sanitization within the browser's rendering engines when processing content in specialized viewing modes. When users activate View Source or Reader mode, the application processes and displays web page elements without sufficient validation of title attributes or other metadata. This allows malicious actors to inject script code within page titles that subsequently executes in the context of the user's browsing session. The flaw operates at the application layer where user-provided content is not properly escaped or filtered before being rendered to the browser interface, creating a direct pathway for malicious script execution.
The operational impact of this vulnerability extends beyond simple script injection as it enables attackers to perform various malicious activities within the user's browsing context. An attacker could potentially execute arbitrary JavaScript code that accesses cookies, session tokens, or other sensitive data stored in the browser. The vulnerability is particularly concerning because it operates within the browser's own interface rather than through external web pages, making it harder to detect and prevent. Users who frequently utilize View Source or Reader modes become especially vulnerable as these features are commonly accessed during normal browsing activities, increasing the attack surface without requiring special user interactions beyond visiting malicious pages.
From a cybersecurity perspective, this vulnerability aligns with CWE-79 which defines cross-site scripting as a weakness where untrusted data is sent to a web browser without proper validation or sanitization. The attack pattern follows typical XSS exploitation methods where malicious input is crafted to execute within the victim's browser context, potentially leading to session hijacking, data theft, or further compromise of the user's system. The ATT&CK framework categorizes this under T1059.007 for scripting languages and T1566 for social engineering techniques, as attackers may use this vulnerability to craft deceptive web pages that appear legitimate while executing malicious code.
Mitigation strategies for CVE-2021-45087 require immediate patching of affected GNOME Web versions to 40.4 or 41.1 respectively, ensuring that all users have access to the security updates. Organizations should implement browser hardening policies that restrict access to potentially vulnerable modes or disable them entirely when not required for specific administrative tasks. Network monitoring solutions should be configured to detect anomalous script execution patterns that might indicate exploitation attempts. Users should be educated about the risks of accessing untrusted websites and the importance of keeping their browser software updated. Additionally, administrators should consider implementing content security policies that limit script execution within browser interfaces and regularly audit browser configurations to ensure that vulnerable features are properly secured or disabled.