CVE-2021-30108 in Feehi
Summary
by MITRE • 05/25/2021
Feehi CMS 2.1.1 is affected by a Server-side request forgery (SSRF) vulnerability. When the user modifies the HTTP Referer header to any url, the server can make a request to it.
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Analysis
by VulDB Data Team • 05/27/2021
The vulnerability identified as CVE-2021-30108 affects Feehi CMS version 2.1.1 and represents a critical server-side request forgery flaw that enables remote attackers to manipulate the application's behavior through crafted HTTP requests. This vulnerability falls under the broader category of insecure direct object references and specifically aligns with CWE-918, which defines server-side request forgery as a condition where an application fails to properly validate and sanitize user-supplied input that influences HTTP requests made by the server. The flaw manifests when the application processes the HTTP Referer header without adequate validation, allowing an attacker to specify arbitrary URLs that the server will attempt to access on behalf of the application.
The technical implementation of this vulnerability occurs within the CMS's request handling mechanism where the application accepts the Referer header value directly and uses it to construct outbound requests without proper sanitization or validation. This creates a dangerous attack surface where malicious actors can leverage the server's network access to probe internal systems, access restricted resources, or even exfiltrate data from behind firewalls. The vulnerability is particularly concerning because it can be exploited through simple HTTP header manipulation, making it accessible to attackers with minimal technical expertise. The server's trust in the Referer header value allows for potential exploitation of internal services that might otherwise be protected by network segmentation or access controls.
From an operational impact perspective, this SSRF vulnerability can lead to severe consequences including unauthorized access to internal network resources, data leakage, and potential compromise of the entire application infrastructure. Attackers can use this flaw to perform reconnaissance activities against internal systems, access sensitive information stored on internal servers, or even establish command and control channels. The vulnerability can be exploited in conjunction with other attack vectors to escalate privileges or gain deeper access to the system. According to ATT&CK framework, this vulnerability maps to T1566.002 - Phishing with Malicious Attachment and T1071.004 - Application Layer Protocol: DNS, as attackers can use the SSRF to bypass network restrictions and access internal resources that would normally be protected.
Mitigation strategies for CVE-2021-30108 should focus on implementing strict input validation and sanitization of all user-supplied headers, particularly the Referer header. Organizations should implement a whitelist approach for allowed URLs or IP addresses that the application is permitted to access, and deploy network segmentation to limit the potential impact of such vulnerabilities. The CMS should be updated to the latest version where this vulnerability has been patched, and administrators should monitor for suspicious network traffic patterns that might indicate exploitation attempts. Additional protective measures include implementing proper header validation, using secure coding practices that prevent direct user input from influencing server-side requests, and deploying web application firewalls that can detect and block suspicious SSRF patterns. The vulnerability demonstrates the importance of validating all external inputs and implementing principle of least privilege for server-side operations to prevent attackers from leveraging trusted application behavior to access unauthorized resources.