CVE-2018-8108 in bui
Summary
by MITRE
The select component in bui through 2018-03-13 has XSS because it performs an escape operation on already-escaped text, as demonstrated by workGroupList text.
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Analysis
by VulDB Data Team • 01/13/2020
The vulnerability identified as CVE-2018-8108 affects the select component within the bui library version prior to 2018-03-13, representing a classic cross-site scripting weakness that arises from improper handling of HTML escaping operations. This flaw occurs when the component processes text that has already been escaped, leading to a situation where double escaping creates a vulnerability that allows malicious scripts to execute in the context of the victim's browser. The specific demonstration involves the workGroupList text field, which exposes the component's failure to properly manage escaped content during rendering operations.
The technical root cause of this vulnerability stems from a fundamental flaw in input sanitization and output encoding logic within the bui select component. When the component encounters text that has already been HTML-escaped, it applies additional escaping operations that inadvertently restore the original script tags or other malicious content. This creates a scenario where attackers can inject malicious payloads that bypass initial security measures, as the system treats already-sanitized content as if it were raw input requiring further protection. The vulnerability falls under CWE-79, which specifically addresses cross-site scripting flaws, and demonstrates the importance of proper context-aware encoding in web applications. The flaw represents a case of improper neutralization of special elements used in a different context, commonly referred to as cross-site scripting.
The operational impact of CVE-2018-8108 extends beyond simple script execution, as it can enable attackers to perform a wide range of malicious activities including session hijacking, data exfiltration, and unauthorized access to sensitive information. When an attacker successfully exploits this vulnerability through the workGroupList text field, they can inject JavaScript code that executes within the victim's browser context, potentially allowing them to steal authentication tokens, access restricted resources, or manipulate the application's behavior. The vulnerability is particularly concerning because it affects a core UI component that is likely used extensively throughout applications, meaning a single exploitation can potentially compromise multiple areas of an application's functionality. This aligns with ATT&CK technique T1059.007 for command and control through scripting languages, where the injected scripts can serve as a foothold for further attack activities.
Mitigation strategies for CVE-2018-8108 should focus on updating to the patched version of the bui library released after March 13, 2018, which addresses the double-escaping logic in the select component. Organizations should also implement proper input validation and output encoding practices that ensure content is encoded appropriately for its intended context without applying redundant escaping operations. The fix typically involves modifying the component's handling of escaped text to recognize when content is already sanitized and avoid applying additional encoding operations that would undermine the security measures. Security teams should conduct thorough code reviews to identify similar patterns in other UI components that might exhibit the same double-escaping behavior, and implement automated testing procedures to detect such vulnerabilities in future development cycles. Additionally, application developers should adopt defense-in-depth strategies including content security policies, regular security assessments, and proper security training to prevent similar issues from arising in custom implementations that may interact with vulnerable libraries.