CVE-2018-10799 in Brave
Summary
by MITRE
A hang issue was discovered in Brave before 0.14.0 (on, for example, Linux). This vulnerability is caused by the mishandling of a long URL formed by window.location+='?\u202a\uFEFF\u202b'; concatenation in a SCRIPT element.
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Analysis
by VulDB Data Team • 02/03/2020
The vulnerability identified as CVE-2018-10799 represents a significant denial of service flaw in the Brave browser version 0.14.0 and earlier releases. This issue manifests as a hang condition that can severely impact user experience and system responsiveness. The vulnerability specifically affects Linux operating systems and demonstrates how seemingly innocuous URL manipulation can lead to critical system instability. The flaw resides in the browser's handling of malformed URL strings that contain specific Unicode characters, creating a scenario where the browser becomes unresponsive and unable to process further user interactions.
The technical root cause of this vulnerability stems from improper input validation and string handling within the browser's URL processing pipeline. When a malicious or malformed URL containing the specific Unicode sequence '\u202a\uFEFF\u202b' is encountered, particularly within a script element context, the browser's rendering engine becomes trapped in an infinite loop or excessive processing state. This Unicode sequence consists of right-to-left embedding characters that cause the browser to incorrectly interpret the URL structure, leading to resource exhaustion and system hang conditions. The vulnerability demonstrates a classic case of insufficient input sanitization and improper error handling in web rendering components.
The operational impact of this vulnerability extends beyond simple browser instability, potentially enabling attackers to perform denial of service attacks against users. An attacker could craft malicious web pages containing the problematic URL construction that would cause any affected Brave browser instance to hang indefinitely, rendering the browser unusable until manual intervention or process termination occurs. This vulnerability particularly affects users who browse untrusted websites, as the hang condition can occur during normal page loading operations. The issue affects the core browser functionality and can potentially be exploited in conjunction with other attack vectors to create more sophisticated compromise scenarios.
Mitigation strategies for CVE-2018-10799 primarily involve upgrading to Brave version 0.14.0 or later, which includes the necessary patches to properly handle the problematic Unicode sequences. System administrators should implement browser update policies that ensure all users maintain current versions of the Brave browser. Additionally, implementing web content filtering solutions that can detect and block malicious URL patterns may provide an additional layer of protection. Organizations should also consider monitoring browser behavior for signs of hanging or unresponsive conditions that could indicate exploitation attempts. The vulnerability aligns with CWE-129, which addresses improper validation of length in input processing, and relates to ATT&CK technique T1499.004 for network denial of service attacks through browser manipulation. Regular security assessments and penetration testing should include verification of browser versions and proper handling of Unicode input sequences to prevent similar vulnerabilities from being exploited in other browser implementations or web applications.