CVE-2018-8046 in Ext JS
Summary
by MITRE
The getTip() method of Action Columns of Sencha Ext JS 4 to 6 before 6.6.0 is vulnerable to XSS attacks, even when passed HTML-escaped data. This framework brings no built-in XSS protection, so the developer has to ensure that data is correctly sanitized. However, the getTip() method of Action Columns takes HTML-escaped data and un-escapes it. If the tooltip contains user-controlled data, an attacker could exploit this to create a cross-site scripting attack, even when developers took precautions and escaped data.
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Analysis
by VulDB Data Team • 02/26/2020
The vulnerability identified as CVE-2018-8046 resides within the Sencha Ext JS framework, specifically affecting versions 4 through 6 before 6.6.0. This issue manifests in the getTip() method of Action Columns, representing a critical security flaw that undermines the framework's intended protection mechanisms. The vulnerability operates on the fundamental principle that developers may implement proper HTML escaping measures to prevent cross-site scripting attacks, yet the framework itself contains a method that automatically reverses these protective measures. This creates a dangerous scenario where even properly sanitized data becomes vulnerable to exploitation through the framework's own internal processing logic.
The technical flaw stems from the getTip() method's behavior of automatically unescaping HTML-escaped data without proper validation or sanitization. When developers implement HTML escaping to protect against XSS attacks, they expect that data will remain safe throughout the application's processing pipeline. However, the Action Columns component's getTip() method explicitly performs HTML unescaping operations on data that was previously escaped, effectively neutralizing the security measures that developers have implemented. This behavior violates the principle of least privilege and demonstrates a classic case of improper input validation where the framework assumes that data passed to it is safe without performing necessary security checks. The vulnerability falls under CWE-79, which specifically addresses Cross-site Scripting flaws, and more particularly aligns with CWE-116, concerning improper encoding or escaping of output.
The operational impact of this vulnerability extends beyond simple data exposure, creating a potential attack vector that can be exploited by malicious actors to execute arbitrary JavaScript code within the context of affected applications. When user-controlled data is passed to tooltip functionality through Action Columns, attackers can craft malicious payloads that will be executed when the tooltip is displayed. This vulnerability is particularly concerning because it operates silently in the background, bypassing traditional security controls that developers might have implemented. The attack surface includes any application using Sencha Ext JS versions within the affected range that implements Action Columns with user-provided tooltip data, potentially affecting web applications across various industries including financial services, healthcare, and government sectors where sensitive data processing occurs.
Mitigation strategies for CVE-2018-8046 require immediate action from system administrators and developers to upgrade to Sencha Ext JS version 6.6.0 or later, which contains the necessary patches to address this vulnerability. Organizations should conduct comprehensive vulnerability assessments to identify all applications utilizing the affected framework versions and prioritize remediation efforts accordingly. Additionally, developers should implement additional input validation layers and consider using Content Security Policy headers as an additional defense mechanism. The ATT&CK framework categorizes this vulnerability under T1203, which involves Exploitation for Client Execution, as it enables attackers to execute malicious code through web browsers. Organizations should also consider implementing web application firewalls and monitoring systems to detect potential exploitation attempts, while ensuring that all user-provided data undergoes proper sanitization before being processed by any framework components that may automatically unescape content.