CVE-2021-28161 in Theia
Summary
by MITRE • 03/13/2021
In Eclipse Theia versions up to and including 1.8.0, in the debug console there is no HTML escaping, so arbitrary Javascript code can be injected.
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Analysis
by VulDB Data Team • 04/01/2021
The vulnerability identified as CVE-2021-28161 affects Eclipse Theia versions 1.8.0 and earlier, specifically within the debug console functionality. This issue represents a critical security flaw that stems from insufficient input validation and output sanitization mechanisms. The debug console serves as a crucial component for developers to interact with and analyze application behavior during the debugging process, making it a prime target for malicious exploitation. The vulnerability manifests when the system fails to properly escape HTML content, creating an environment where attacker-controlled input can be interpreted as executable JavaScript code rather than benign text.
The technical flaw resides in the lack of proper HTML escaping mechanisms within the debug console's rendering process. When debug output contains user-supplied data that includes HTML or JavaScript characters, the system does not adequately sanitize this input before displaying it to the user. This absence of input validation creates a classic cross-site scripting vulnerability where malicious code can be injected and executed within the context of the user's browser session. The vulnerability is categorized under CWE-79 as Improper Neutralization of Input During Web Page Generation, which specifically addresses the failure to properly escape or filter user-controllable data that is subsequently rendered in web-based interfaces. The flaw allows attackers to inject arbitrary JavaScript code that can execute with the privileges of the victim user, potentially leading to complete session hijacking or data exfiltration.
The operational impact of this vulnerability extends beyond simple code injection, as it can be leveraged to compromise the entire development environment. Attackers can exploit this vulnerability to execute malicious scripts that may steal session cookies, redirect users to phishing sites, or even download and execute additional malware on the victim's machine. In a development context where Theia is used for debugging applications, this vulnerability becomes particularly dangerous as it can be exploited during the debugging process when developers might be viewing potentially malicious output from applications being debugged. The attack surface is further expanded because the debug console is typically used by developers with elevated privileges and access to sensitive development environments. This vulnerability aligns with ATT&CK technique T1566.001 as it represents a form of credential access through social engineering and phishing, where attackers can establish persistent access through the execution of malicious JavaScript code.
Mitigation strategies for this vulnerability require immediate remediation through upgrading to a patched version of Eclipse Theia where proper HTML escaping has been implemented. Organizations should ensure that all instances of Theia are updated to version 1.9.0 or later, where this vulnerability has been addressed through proper input sanitization and output encoding mechanisms. Additionally, administrators should implement strict input validation policies for all user-supplied data that may be displayed in console or web-based interfaces. The solution should include comprehensive HTML escaping of all output, particularly in debug contexts where raw data from applications being debugged may contain malicious content. Security teams should also consider implementing content security policies that restrict script execution within the Theia environment, providing an additional layer of defense against potential exploitation attempts. Regular security audits and penetration testing should be conducted to identify similar vulnerabilities in other components of the development ecosystem, ensuring comprehensive protection against similar cross-site scripting threats.