CVE-2021-44667 in Nacos
Summary
by MITRE • 03/11/2022
A Cross Site Scripting (XSS) vulnerability exists in Nacos 2.0.3 in auth/users via the (1) pageSize and (2) pageNo parameters.
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Analysis
by VulDB Data Team • 03/16/2022
The CVE-2021-44667 vulnerability represents a critical cross site scripting flaw within the Nacos service discovery and configuration management platform version 2.0.3. This vulnerability specifically affects the authentication and user management functionality of the system, creating a pathway for malicious actors to execute arbitrary scripts within the context of a victim's browser session. The vulnerability stems from insufficient input validation and sanitization of user-supplied parameters within the authentication endpoint, particularly affecting the pageSize and pageNo parameters that control pagination of user listings. The affected Nacos version represents a widely deployed configuration management solution used by organizations for microservices architectures, making this vulnerability particularly concerning given the platform's role in managing critical service configurations and authentication credentials. This XSS vulnerability allows attackers to inject malicious scripts into user interfaces that are rendered by the affected system, potentially leading to session hijacking, privilege escalation, or data exfiltration from authenticated user sessions.
The technical exploitation of this vulnerability occurs through manipulation of the pageSize and pageNo parameters in the authentication/users endpoint URL. When these parameters are submitted with malicious script payloads, the Nacos application fails to properly sanitize or escape the input before rendering it within the user interface. This failure in input validation creates a classic XSS attack vector where attackers can inject script code that executes in the context of legitimate user sessions. The vulnerability manifests in the application's user management interface where pagination controls are displayed, allowing attackers to craft URLs that include malicious JavaScript payloads within these parameters. The vulnerability is classified as a reflected XSS issue since the malicious code is reflected back to users through the application's response, typically in the pagination controls or user listing displays. This flaw aligns with CWE-79 which specifically addresses cross-site scripting vulnerabilities in web applications, and follows the patterns described in the OWASP Top Ten as a critical web application security risk.
The operational impact of CVE-2021-44667 extends beyond simple script execution, potentially enabling attackers to escalate privileges within the Nacos system. An attacker who successfully exploits this vulnerability could gain access to user accounts with elevated privileges, allowing them to modify configuration data, create new users, or access sensitive system information. The attack surface is particularly dangerous in environments where Nacos serves as a central configuration management point for microservices, as compromise of this system could lead to widespread service disruption or data breaches. The vulnerability is especially concerning because it affects the authentication and user management components, which are fundamental to system security. Attackers could leverage this vulnerability to establish persistent access to the Nacos system, potentially using it as a foothold for further attacks within the broader infrastructure. The impact is amplified when considering that Nacos is often used in production environments with sensitive configuration data, making this vulnerability a significant threat to enterprise security. This vulnerability also aligns with ATT&CK technique T1566 which covers social engineering and manipulation of web applications, and T1078 which addresses valid accounts and legitimate credentials.
Mitigation strategies for CVE-2021-44667 should begin with immediate patching of affected Nacos instances to version 2.0.4 or later, which contains the necessary input validation fixes. Organizations should implement comprehensive input sanitization measures at the application level, ensuring that all user-supplied parameters are properly escaped and validated before processing. Network-level protections such as web application firewalls should be deployed to detect and block malicious payloads targeting these specific parameters. Security teams should conduct thorough vulnerability assessments of all Nacos installations within their environment, particularly focusing on authentication endpoints and user management interfaces. The implementation of content security policies can provide additional protection against script execution, while regular security monitoring should be established to detect anomalous behavior in user management activities. Organizations should also consider implementing multi-factor authentication for Nacos administrative accounts and establishing strict access controls for the configuration management system. Regular security training for system administrators on recognizing and responding to XSS attacks is essential, as well as maintaining up-to-date security patches across all deployed components of the Nacos platform to prevent similar vulnerabilities from being exploited.