CVE-2026-44583 in Paymenter
Summary
by MITRE • 07/21/2026
Paymenter is a free and open-source webshop solution for management of hosting services. In versions prior to 1.5.0, the PayPal webhook endpoint /extensions/paypal/webhook processes the PAYPAL-CERT-URL HTTP header without validation, allowing attackers to control server-side HTTP request destinations. This value is passed directly into a server-side HTTP request via file_get_contents, allowing attackers to control the destination of the request. No allowlist, validation, or signature verification is applied to the header before usage. As a result, the application can be coerced into performing HTTP requests to attacker-controlled or internal network destinations. This vulnerability allows remote unauthenticated attackers to induce server-side HTTP GET requests to arbitrary external or internal endpoints. Depending on network configuration, this may lead to: blind SSRF to external attacker-controlled systems, and potential access to internal network services No direct response data is returned to the attacker (blind SSRF), but the issue may still enable sensitive network probing or data exfiltration via side channels. This issue has been fixed in version 1.5.0.
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Analysis
by VulDB Data Team • 07/21/2026
Paymenter webshop solution contains a critical server-side request forgery vulnerability in its PayPal webhook endpoint implementation. The flaw exists in versions prior to 1.5.0 where the /extensions/paypal/webhook endpoint processes the PAYPAL-CERT-URL HTTP header without any validation mechanisms. This header is passed directly to the file_get_contents function, creating a dangerous attack vector that allows remote unauthenticated adversaries to control where the application makes outbound HTTP requests. The vulnerability represents a classic blind server-side request forgery scenario as defined by CWE-918 and aligns with ATT&CK technique T1102 for web service tunneling.
The technical implementation of this vulnerability stems from the complete absence of input validation, allowlisting, or signature verification for the PAYPAL-CERT-URL header. When an attacker sends a malicious request to the webhook endpoint, they can inject arbitrary values into this header that get processed server-side without any sanitization. This creates a pathway for attackers to force the vulnerable application to make HTTP GET requests to any destination they choose, whether external attacker-controlled systems or internal network services within the same network segment. The lack of any defensive controls around this header processing makes the vulnerability particularly dangerous as it operates entirely in a blind mode without direct response data being returned to the attacker.
The operational impact of this vulnerability extends beyond simple network probing as demonstrated by the potential for sensitive data exfiltration through side channels and internal service enumeration. While the attack is classified as blind SSRF since no direct response data flows back to the attacker, the ability to initiate requests to internal systems creates opportunities for attackers to map network topology, probe internal services, and potentially discover additional vulnerabilities within the internal infrastructure. This type of vulnerability commonly enables further attacks such as internal port scanning, service discovery, and may facilitate access to sensitive internal resources that would otherwise be isolated from external access.
Organizations using Paymenter versions prior to 1.5.0 should immediately implement mitigations including updating to the patched version where the vulnerability has been resolved through proper input validation of the PAYPAL-CERT-URL header. Additional defensive measures include implementing network-level restrictions such as firewall rules to prevent outbound connections from the web server to internal networks, and deploying web application firewalls to monitor and block suspicious header values. The fix implemented in version 1.5.0 demonstrates proper security practices by introducing validation mechanisms that ensure all external references are properly verified before being used in server-side requests, thereby preventing the exploitation path that existed in earlier versions of the software.