CVE-2017-6900 in NetMan 204
Summary
by MITRE
An issue was discovered in Riello NetMan 204 14-2 and 15-2. The issue is with the login script and wrongpass Python script used for authentication. When calling wrongpass, the variables $VAL0 and $VAL1 should be enclosed in quotes to prevent the potential for Bash command injection. Further to this, VAL0 and VAL1 should be sanitised to ensure they do not contain malicious characters. Passing it the username of '-' will cause it to time out and log the user in because of poor error handling. This will log the attacker in as an administrator where the telnet / ssh services can be enabled, and the credentials for local users can be reset. Also, login.cgi accepts the username as a GET parameter, so login can be achieved by browsing to the /cgi-bin/login.cgi?username=-%20a URI.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 10/17/2023
The vulnerability identified in Riello NetMan 204 14-2 and 15-2 systems represents a critical authentication bypass flaw that stems from improper input validation and command execution handling within the login authentication scripts. This issue affects the login script and wrongpass Python script components that govern user authentication processes, creating a pathway for unauthorized administrative access to network management interfaces. The vulnerability resides in the improper handling of user input variables VAL0 and VAL1, which are processed without adequate sanitization or proper quoting mechanisms that would prevent shell command injection attacks. According to CWE-78, this vulnerability directly maps to improper neutralization of special elements used in OS commands, while also aligning with CWE-20 for improper input validation and CWE-287 for improper authentication mechanisms.
The technical implementation of this vulnerability exploits multiple layers of authentication weakness that compound to create a complete bypass scenario. When the wrongpass script is invoked, the variables VAL0 and VAL1 are passed to shell commands without proper shell escaping or quoting, creating opportunities for command injection attacks. The specific exploitation technique leverages the fact that passing a username of "-" causes the system to time out and incorrectly grant administrative access due to flawed error handling logic. This particular attack vector demonstrates poor input validation where the system fails to properly sanitize user-supplied input, allowing malicious payloads to be interpreted as command parameters rather than simple username values. The GET parameter handling in login.cgi further amplifies this issue by exposing the authentication endpoint to simple browser-based exploitation without requiring specialized tools or complex attack chains.
The operational impact of this vulnerability extends far beyond simple unauthorized access, as successful exploitation grants attackers full administrative privileges within the network management system. Once authenticated as an administrator, attackers can enable telnet and ssh services, effectively creating persistent access points that bypass traditional network security controls. Additionally, the ability to reset local user credentials provides attackers with complete control over the system's user management functionality, potentially allowing them to establish backdoor accounts or disable legitimate access mechanisms. This vulnerability represents a significant risk to network infrastructure security, as it allows attackers to assume administrative control of critical network management equipment. The combination of command injection capabilities with credential reset functionality creates a comprehensive attack surface that can be leveraged for persistent network compromise, lateral movement, and potential data exfiltration from within the network perimeter.
Mitigation strategies for this vulnerability must address both the immediate code-level issues and implement broader security controls to prevent similar flaws from occurring in the future. The primary fix involves properly quoting all variables passed to shell commands within the wrongpass script, ensuring that VAL0 and VAL1 values are enclosed in appropriate quotes to prevent command injection. Input sanitization must be implemented to filter out potentially malicious characters and prevent special shell metacharacters from being interpreted as commands. Additionally, the error handling logic should be strengthened to properly validate all user inputs and prevent the system from incorrectly granting access based on malformed input. The use of GET parameters for authentication should be eliminated or properly validated, as this creates unnecessary exposure to simple exploitation techniques. Organizations should also implement proper authentication logging and monitoring to detect unauthorized access attempts, while following ATT&CK framework guidance for credential access and privilege escalation techniques to better understand and defend against such attacks. Network segmentation and access control measures should be implemented to limit the impact of successful exploitation, while regular security assessments and code reviews should be conducted to identify and remediate similar vulnerabilities in other network management systems.