CVE-2018-11396 in Web
Summary
by MITRE
ephy-session.c in libephymain.so in GNOME Web (aka Epiphany) through 3.28.2.1 allows remote attackers to cause a denial of service (application crash) via JavaScript code that triggers access to a NULL URL, as demonstrated by a crafted window.open call.
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Analysis
by VulDB Data Team • 02/08/2020
The vulnerability identified as CVE-2018-11396 affects GNOME Web, also known as Epiphany, version 3.28.2.1 and earlier. This represents a critical denial of service flaw that can be exploited remotely through malicious JavaScript code execution. The issue resides within the ephy-session.c component of the libephymain.so library, which forms a core part of the web browser's session management functionality. The vulnerability specifically manifests when JavaScript code attempts to access a NULL URL through a crafted window.open call, leading to an application crash that effectively renders the browser unusable.
This vulnerability falls under the category of improper input validation and memory safety issues, with direct implications for software robustness and security. The technical flaw occurs when the browser's session handling mechanism fails to properly validate URL parameters before attempting to process them. When a NULL URL is passed through JavaScript's window.open method, the underlying ephy-session.c code does not adequately handle this edge case, resulting in a null pointer dereference that crashes the entire application. This behavior aligns with CWE-476, which describes null pointer dereference vulnerabilities, and demonstrates how insufficient input validation can lead to application instability.
The operational impact of this vulnerability extends beyond simple service disruption, as it provides attackers with a reliable method to crash the GNOME Web browser remotely. This makes it particularly dangerous in environments where users might encounter malicious websites or be tricked into executing crafted JavaScript code. The vulnerability affects any system running affected versions of GNOME Web, including desktop environments that utilize this browser as their default web client. Attackers can leverage this flaw through various vectors including malicious websites, phishing campaigns, or compromised web content that triggers the vulnerable JavaScript code path. The crash occurs during normal browsing operations, making it difficult for users to distinguish between legitimate application behavior and malicious exploitation attempts.
Mitigation strategies for this vulnerability should focus on immediate patching of affected systems, as the primary resolution involves updating to version 3.28.2.2 or later where the issue has been addressed. Organizations should implement comprehensive patch management procedures to ensure all instances of GNOME Web are updated promptly. Additionally, browser hardening measures such as disabling JavaScript execution in untrusted contexts or implementing content security policies can provide additional defense in depth. Security monitoring should include detection of suspicious window.open calls and unusual URL patterns that might indicate exploitation attempts. From an ATT&CK framework perspective, this vulnerability maps to T1211 - Exploitation for Defense Evasion and T1499 - Endpoint Denial of Service, as it enables attackers to disrupt services and potentially evade detection through application crashes. System administrators should also consider implementing browser sandboxing mechanisms and restricting access to potentially malicious websites through network-level controls. The vulnerability demonstrates the importance of proper error handling in web browser components and highlights the need for robust input validation in all user-facing applications to prevent similar issues from arising in the future.