CVE-2020-21639 in RG-UAC 6000-E50
Summary
by MITRE • 11/17/2021
Ruijie RG-UAC 6000-E50 commit 9071227 was discovered to contain a cross-site scripting (XSS) vulnerability via the rule_name parameter. This vulnerability allows attackers to execute arbitrary web scripts or HTML via a crafted payload.
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Analysis
by VulDB Data Team • 11/22/2021
The CVE-2020-21639 vulnerability represents a critical cross-site scripting flaw identified in Ruijie RG-UAC 6000-E50 network security appliances running commit version 9071227. This vulnerability resides within the web interface of the device and specifically affects the rule_name parameter handling mechanism. The issue stems from inadequate input validation and output encoding practices within the appliance's user authentication and access control management system. Security researchers discovered that when users interact with the rule management functionality, the system fails to properly sanitize user-supplied input data, creating an exploitable condition that enables malicious actors to inject and execute arbitrary JavaScript code within the context of authenticated sessions. The vulnerability affects the device's administrative web interface, which is typically accessed by network administrators to configure access control rules and security policies.
The technical exploitation of this XSS vulnerability occurs through the manipulation of the rule_name parameter, which is used to define access control rules within the appliance's management console. When an attacker crafts a malicious payload containing script code and submits it through this parameter, the vulnerable system fails to properly encode or escape the input before rendering it in the web interface. This creates a persistent cross-site scripting condition where the malicious code executes in the browser of any user who views the affected page, particularly administrators who manage the access control rules. The vulnerability is classified as a stored XSS attack since the malicious payload is stored within the device's configuration and executed whenever the affected rule is displayed. This type of vulnerability falls under CWE-79 which specifically addresses Cross-Site Scripting flaws and aligns with ATT&CK technique T1566.001 for Initial Access through spearphishing attachments or links.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with the ability to escalate privileges and potentially gain unauthorized access to the network security appliance. An attacker who successfully exploits this vulnerability can establish persistent access to the device's administrative interface, modify access control policies, create backdoor accounts, or even redirect traffic through the compromised appliance. The vulnerability affects the integrity and confidentiality of the network security controls, as it allows unauthorized parties to manipulate the access control mechanisms that are meant to protect the network infrastructure. Given that the device operates as a user authentication and access control system, successful exploitation could lead to complete network compromise, as attackers could bypass authentication mechanisms and gain unrestricted access to network resources. The impact is particularly severe because the vulnerability affects the core functionality of the appliance, which is responsible for enforcing security policies and controlling user access to network resources.
Mitigation strategies for CVE-2020-21639 should focus on immediate patching and configuration hardening measures. Network administrators should prioritize updating the Ruijie RG-UAC 6000-E50 appliances to the latest firmware version that addresses this vulnerability, as provided by the vendor. In the absence of an official patch, administrators should implement input validation measures at the network perimeter and consider disabling unnecessary web interface access to reduce attack surface. The appliance configuration should enforce strict output encoding for all user-supplied parameters, particularly those used in rule management functions. Network segmentation and access control measures should be strengthened to limit the potential impact of successful exploitation attempts. Security monitoring should be enhanced to detect unusual access patterns or attempts to manipulate rule configurations. Additionally, regular security assessments should be conducted to identify similar vulnerabilities in other network security appliances within the organization. The vulnerability highlights the importance of proper input validation and output encoding practices in web applications, as mandated by OWASP Top 10 and NIST cybersecurity frameworks, which emphasize the need for robust application security controls in network infrastructure devices.