CVE-2026-83543 in Greenshift Plugin
Summary
by MITRE • 09/05/2026
The Greenshift WordPress plugin before 13.2.0 does not validate a user-supplied URL before fetching it server-side, allowing users with contributor-level access and above to make the server issue requests to arbitrary hosts and read the response.
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Analysis
by VulDB Data Team • 09/05/2026
The vulnerability identified in versions of the Greenshift WordPress plugin prior to 13.2.0 represents a critical Server-Side Request Forgery (SSRF) flaw rooted in insufficient input validation on user-supplied URLs. This security defect allows authenticated attackers with contributor-level access or higher privileges to manipulate server-side behavior by injecting maliciously crafted Uniform Resource Locators into specific plugin functionalities that process external resources. By exploiting this lack of sanitization, an attacker can compel the web application's backend processes to initiate HTTP requests to arbitrary destinations controlled by the adversary rather than legitimate third-party services intended for normal operation. This capability effectively bypasses standard client-side security controls and leverages the server's network permissions and identity to interact with internal or external networks that would otherwise be inaccessible from a direct browser context.
From a technical perspective, the core issue lies in the absence of rigorous validation mechanisms such as allow-listing permitted domains, enforcing protocol restrictions, or implementing DNS rebinding protections before the application executes the fetch operation. When the plugin processes these unvalidated inputs, it fails to distinguish between trusted internal endpoints and external malicious targets. This allows an attacker to probe internal network infrastructure, access cloud metadata services that often contain sensitive authentication credentials, or interact with local development servers running on localhost interfaces. The vulnerability is particularly dangerous because it operates at the server level, meaning the requests originate from a privileged position within the application's hosting environment, potentially bypassing firewall rules and intrusion detection systems designed to monitor external traffic patterns rather than internal application logic flows.
The operational impact of this SSRF vulnerability extends beyond simple data exfiltration or network reconnaissance. An attacker with contributor-level access can leverage this flaw to perform port scanning against internal services, retrieve sensitive configuration files from local storage if exposed via file protocols, or interact with administrative interfaces of other applications hosted on the same server infrastructure. In cloud environments, accessing instance metadata endpoints such as those found in AWS EC2 or Google Cloud Platform can lead to full account compromise by stealing temporary security credentials. Furthermore, this vulnerability facilitates blind SSRF attacks where the attacker may not immediately see the response but can infer information based on timing differences or error messages, aiding in further exploitation of adjacent systems within the network topology.
This flaw aligns with Common Weakness Enumeration identifier CWE-918, which specifically addresses Server-Side Request Forgery resulting from improper validation of user-supplied URLs for server-side requests. Additionally, it maps to MITRE ATT&CK technique T1571, indicating a non-standard application layer protocol or service being abused to establish command and control channels or exfiltrate data through legitimate-looking network traffic generated by the compromised application itself. The privilege requirement of contributor-level access means that while not immediately exploitable by unauthenticated users, it poses a significant risk in environments where user registration is open or where lower-privileged accounts have been compromised through phishing or credential stuffing attacks.
Mitigation strategies must prioritize immediate patching to version 13.2.0 or later, which addresses the input validation gaps identified during development. For organizations unable to upgrade immediately due to compatibility constraints with other plugins or custom code modifications, temporary mitigations should include implementing a web application firewall rule that restricts outbound HTTP requests from the WordPress process to only known and approved domains. Network-level controls such as egress filtering can also be employed to block access to private IP ranges and cloud metadata endpoints from the server hosting the vulnerable plugin. Additionally, developers should enforce strict allow-listing of permitted URLs in future code updates, ensuring that any user-supplied input is validated against a predefined list of trusted domains before being passed to network request functions. Regular security audits focusing on SSRF vectors are recommended to identify similar patterns across other plugins and custom themes within the WordPress ecosystem.