CVE-2020-5142 in SonicOS
Summary
by MITRE • 10/12/2020
A stored cross-site scripting (XSS) vulnerability exists in the SonicOS SSLVPN web interface. A remote unauthenticated attacker is able to store and potentially execute arbitrary JavaScript code in the firewall SSLVPN portal. This vulnerability affected SonicOS Gen 5 version 5.9.1.7, 5.9.1.13, Gen 6 version 6.5.4.7, 6.5.1.12, 6.0.5.3, SonicOSv 6.5.4.v and Gen 7 version SonicOS 7.0.0.0.
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Analysis
by VulDB Data Team • 11/18/2020
The vulnerability identified as CVE-2020-5142 represents a critical stored cross-site scripting flaw within the SonicOS SSLVPN web interface, exposing organizations to significant security risks through remote code execution capabilities. This vulnerability specifically targets the firewall's SSLVPN portal, creating an attack vector that allows unauthenticated remote adversaries to inject malicious JavaScript code into the system. The flaw exists in multiple versions of SonicOS across different generations, including Gen 5 versions 5.9.1.7 and 5.9.1.13, Gen 6 versions 6.5.4.7, 6.5.1.12, and 6.0.5.3, SonicOSv 6.5.4.v, and Gen 7 version SonicOS 7.0.0.0, indicating a widespread impact across the SonicWall product line. The stored nature of this vulnerability means that malicious code injected by an attacker persists within the system and can be executed whenever legitimate users access the affected web interface, making it particularly dangerous for organizations relying on SSLVPN for remote access.
The technical implementation of this vulnerability stems from inadequate input validation and output encoding within the SonicOS SSLVPN web interface components. When users interact with the SSLVPN portal, the system fails to properly sanitize user-supplied input before storing and rendering it within web pages, creating an environment where attacker-controlled JavaScript code can be permanently embedded in the application's data storage. This flaw directly maps to CWE-79, which defines cross-site scripting vulnerabilities as weaknesses that occur when an application includes untrusted data in a new web page without proper validation or escaping, or without the appropriate context-specific escaping. The vulnerability's classification as a stored XSS flaw means that the malicious payload is stored on the server and executed against subsequent users who access the affected functionality, rather than requiring immediate interaction with the malicious input. Attackers can exploit this by crafting malicious input through various interface elements such as username fields, login forms, or other user input mechanisms within the SSLVPN portal, which are then stored and subsequently executed in the context of other users' browsers.
The operational impact of CVE-2020-5142 extends far beyond simple data theft or session hijacking, as it provides attackers with persistent access to the network infrastructure through the firewall's SSLVPN portal. Once successfully exploited, the stored JavaScript code can be used to establish persistent backdoors, redirect users to malicious sites, steal session cookies, or even escalate privileges within the network. This vulnerability creates a persistent threat vector that can remain active for extended periods, potentially allowing attackers to maintain access even after initial exploitation attempts. The attack surface is particularly concerning for organizations using SonicWall firewalls for remote access, as it directly undermines the security posture of their network perimeter. The vulnerability can be leveraged for advanced persistent threat campaigns where attackers establish long-term access to the network infrastructure, potentially enabling them to move laterally across the network, exfiltrate sensitive data, or deploy additional malware. Organizations may experience cascading security failures as the compromised SSLVPN portal can serve as a launching point for broader network attacks, making the impact of this vulnerability significantly more severe than typical XSS flaws.
Organizations affected by CVE-2020-5142 should implement immediate mitigations including applying the vendor-provided security patches and updates released by SonicWall to address the specific XSS vulnerability. Network segmentation and monitoring should be enhanced to detect anomalous behavior that might indicate exploitation attempts, with particular attention to unusual login patterns or traffic originating from SSLVPN connections. Access controls should be reviewed and strengthened, including implementing multi-factor authentication for SSLVPN access and limiting the scope of privileges granted to users accessing through the SSLVPN portal. The vulnerability's alignment with ATT&CK technique T1071.004 for application layer protocol usage demonstrates that attackers may leverage the compromised portal to establish command and control channels, making comprehensive network monitoring essential. Security teams should also consider implementing web application firewalls and content security policies to provide additional defense layers against XSS exploitation attempts. Regular security assessments and vulnerability scanning should be conducted to identify similar issues within the broader network infrastructure, as the presence of this vulnerability suggests potential weaknesses in input validation and output encoding practices that may exist elsewhere in the system. The remediation process should include thorough testing of the applied patches to ensure they do not introduce compatibility issues with existing network services while maintaining the security posture against this specific stored XSS vulnerability.