CVE-2017-0889 in Paperclip Ruby Gem
Summary
by MITRE
Paperclip ruby gem version 3.1.4 and later suffers from a Server-SIde Request Forgery (SSRF) vulnerability in the Paperclip::UriAdapter class. Attackers may be able to access information about internal network resources.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 01/10/2023
The CVE-2017-0889 vulnerability resides within the Paperclip ruby gem, a widely used file attachment library for ruby on rails applications. This particular flaw affects versions 3.1.4 and later, making it a significant concern for applications that rely on paperclip for handling file uploads. The vulnerability manifests in the Paperclip::UriAdapter class, which is responsible for processing URIs when fetching remote files for attachment. The core issue stems from insufficient validation of URI schemes and hostnames, allowing malicious actors to craft requests that bypass normal network restrictions and access internal resources that should remain protected.
The technical exploitation of this server-side request forgery vulnerability occurs when an application using paperclip processes a URI that points to an internal network resource. Attackers can construct malicious URIs that target internal services, databases, or other networked components that are normally inaccessible from the internet. The vulnerability essentially allows an attacker to make arbitrary HTTP requests from the server hosting the vulnerable application, potentially enabling them to probe internal networks, access sensitive data, or even escalate their privileges. This represents a classic SSRF flaw that aligns with CWE-918, which specifically addresses server-side request forgery vulnerabilities where applications fail to properly validate or sanitize user-provided URIs.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable attackers to perform reconnaissance activities against internal systems. Applications utilizing paperclip for processing external file references become potential entry points for attackers seeking to map internal network topology or access restricted resources. The vulnerability is particularly dangerous in environments where applications run with elevated privileges or where internal services are not properly isolated from external access. From an attacker's perspective, this vulnerability can be leveraged to perform network scanning, access internal APIs, or even potentially exploit other vulnerabilities within the internal network that are normally protected by firewalls or access controls. The implications align with ATT&CK technique T1046, which covers network service scanning, and T1071.004, which involves application layer protocol: web protocols.
Mitigation strategies for CVE-2017-0889 require immediate action to upgrade paperclip to versions that address the SSRF vulnerability, typically those released after the vulnerability disclosure. Organizations should implement strict URI validation mechanisms that restrict allowed schemes and hostnames, ensuring that only trusted external resources can be accessed through the application. Network segmentation and firewall rules should be configured to prevent outbound requests to internal network resources from application servers. Additionally, implementing proper input sanitization and using allowlists for URI schemes such as http and https while blocking internal schemes like file or ftp can significantly reduce the attack surface. Security teams should also consider implementing network monitoring to detect unusual outbound requests that may indicate exploitation attempts, as well as conducting thorough code reviews to identify any other potential sources of SSRF vulnerabilities within the application stack.