CVE-2017-15644 in Webmin
Summary
by MITRE
SSRF exists in Webmin 1.850 via the PATH_INFO to tunnel/link.cgi, as demonstrated by a GET request for tunnel/link.cgi/http://INTRANET-IP:8000.
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Analysis
by VulDB Data Team • 07/08/2024
The vulnerability identified as CVE-2017-15644 represents a critical server-side request forgery flaw in Webmin version 1.850 that allows attackers to bypass authentication mechanisms and access internal network resources. This vulnerability specifically affects the tunnel/link.cgi component within the Webmin web interface, which processes PATH_INFO parameters without adequate validation or sanitization. The flaw enables unauthorized users to make requests to internal services that would normally be restricted by network segmentation policies, effectively creating a backdoor for internal network reconnaissance and exploitation.
The technical implementation of this vulnerability stems from improper input validation within the Webmin application's handling of HTTP requests. When a GET request is made to tunnel/link.cgi with a URL-encoded path parameter, the application fails to properly validate or sanitize the input before using it in subsequent network requests. This allows attackers to craft malicious requests that can traverse internal network boundaries and access services running on internal IP addresses and ports. The vulnerability operates at the application layer and demonstrates a classic lack of proper access control and input validation mechanisms. According to CWE-918, this represents a Server-Side Request Forgery vulnerability where the application receives a request for a resource that it then forwards to another system, but fails to properly validate the destination or source of that request.
The operational impact of CVE-2017-15644 is severe and multifaceted, potentially enabling attackers to perform extensive internal network reconnaissance, access sensitive internal services, and escalate privileges within the compromised environment. An attacker could use this vulnerability to scan internal network ports, access internal web applications, retrieve sensitive data from internal databases, or even pivot to other systems within the network. The vulnerability specifically affects systems where Webmin is installed with default configurations, making it particularly dangerous in enterprise environments where administrative interfaces are often exposed to untrusted networks. This flaw aligns with ATT&CK technique T1071.004 for application layer protocol: DNS, as the vulnerability allows for protocol manipulation and information gathering through the Webmin interface.
Mitigation strategies for this vulnerability should include immediate patching of Webmin to version 1.860 or later, which contains the necessary fixes for the SSRF vulnerability. Network administrators should also implement proper network segmentation and firewall rules to restrict access to Webmin interfaces, ensuring that administrative access is only available from trusted networks. Additional protective measures include implementing web application firewalls that can detect and block suspicious requests to tunnel/link.cgi endpoints, conducting regular security audits of administrative interfaces, and disabling unnecessary services or features within Webmin that could contribute to the attack surface. Organizations should also consider implementing monitoring and logging for unusual network requests that may indicate exploitation attempts, as this vulnerability can be used for both reconnaissance and active exploitation phases of an attack lifecycle.