CVE-2017-2339 in ScreenOS
Summary
by MITRE
A persistent cross site scripting vulnerability in NetScreen WebUI of Juniper Networks Juniper NetScreen Firewall+VPN running ScreenOS allows a user with the 'security' role to inject HTML/JavaScript content into the management session of other users including the administrator. This enables the lower-privileged user to effectively execute commands with the permissions of an administrator. This issue affects Juniper Networks ScreenOS 6.3.0 releases prior to 6.3.0r24 on SSG Series. No other Juniper Networks products or platforms are affected by this issue.
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Analysis
by VulDB Data Team • 12/12/2022
This vulnerability represents a critical persistent cross site scripting flaw in the NetScreen WebUI interface of Juniper Networks firewalls, specifically affecting ScreenOS 6.3.0 releases before 6.3.0r24 on SSG Series devices. The vulnerability stems from inadequate input validation and output encoding mechanisms within the web management interface, allowing malicious users with the 'security' role to inject malicious HTML and JavaScript content into session management components. The flaw operates as a persistent XSS attack where injected code is stored on the server and subsequently executed in the contexts of other users' browser sessions, particularly targeting administrator accounts with elevated privileges.
The technical exploitation of this vulnerability occurs through the manipulation of web interface parameters that are not properly sanitized before being rendered back to users. When a user with the 'security' role accesses certain management functions, the system fails to adequately validate or escape user-supplied input, creating an environment where malicious payloads can be stored and executed in the context of other users' sessions. This persistent nature means that the injected code remains active even after the initial request, continuously affecting any user who views the affected pages. The vulnerability directly maps to CWE-79 - Improper Neutralization of Input During Web Page Generation, which is a fundamental web application security weakness that enables cross site scripting attacks.
The operational impact of this vulnerability is severe as it allows privilege escalation from the 'security' role to full administrative privileges without requiring additional authentication or authorization. A lower-privileged user can effectively execute commands with administrator permissions by injecting malicious code that executes in the administrator's browser session, potentially leading to complete system compromise. This attack vector enables unauthorized access to sensitive configuration data, modification of firewall rules, network access control policies, and the ability to establish persistent backdoors within the network infrastructure. The vulnerability affects the core management interface of the firewall, which is critical for network security operations and makes the entire network infrastructure potentially vulnerable to unauthorized manipulation.
Mitigation strategies should focus on immediate patch deployment to ScreenOS 6.3.0r24 or later versions that address the input validation flaws in the web interface. Network administrators should implement additional security controls including strict input validation at multiple layers, enhanced session management protocols, and regular security auditing of web interface components. The principle of least privilege should be enforced by limiting the 'security' role permissions and implementing role-based access controls that prevent lower-privileged users from injecting content that could affect administrator sessions. Organizations should also consider implementing web application firewalls to monitor and filter malicious payloads, conduct regular security assessments of web interfaces, and establish incident response procedures for detecting and responding to persistent XSS attacks. This vulnerability aligns with attack techniques described in the ATT&CK framework under T1059 - Command and Scripting Interpreter and T1078 - Valid Accounts, as it enables attackers to leverage compromised sessions to execute commands with elevated privileges.