CVE-2026-44583 Paymenter vulnerability
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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Paymenter should be reviewed and updated if it matches the affected versions. The recommended fix is to apply the vendor-supported patched version or the mitigation steps below, then retest the public website with Fixnx.
Who is affected
Affected versions
- < 1.5.0
Fixed versions
- Apply the latest vendor-supported patched version.
How to fix it
CVE-2026-44583 affects Paymenter and involves server-side request forgery. Successful exploitation may make the server contact internal services or expose data that should not be reachable externally. Treat this as a high-priority fix, especially when the affected component or endpoint is reachable by untrusted users. Upgrade Paymenter to 1.5.0 or a later vendor-supported fixed release.
- Inventory every deployment, device, package, plugin, container, build, and environment that uses Paymenter.
- Compare the installed version with the recorded affected range: < 1.5.0.
- Upgrade Paymenter to 1.5.0 or a later vendor-supported fixed release.
- Until patched, restrict URL inputs and block outbound access to private, loopback, link-local, and cloud-metadata addresses.
- Review configuration, roles, tokens, network paths, and exposed endpoints connected to Paymenter; remove access that is not required.
- Review proxy, DNS, firewall, cloud-metadata, and application logs for requests to internal, loopback, link-local, or unusual external addresses.
- If exploitation is suspected, isolate affected assets, preserve evidence, rotate exposed credentials or keys, restore trusted data, and rebuild compromised systems before returning them to service.
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Verify the fix
- Confirm every affected asset now runs the fixed vendor-supported release or has the documented mitigation for CVE-2026-44583 in place.
- Use a safe regression test to confirm the affected server-side request forgery path no longer produces the vulnerable behavior.
- Confirm temporary access controls, endpoint restrictions, network blocks, and least-privilege settings remain effective after the update.
- Review post-remediation logs and rerun Fixnx plus the relevant package, dependency, firmware, browser, or product-specific security check.
- Document affected assets, versions, changes, validation evidence, reviewed logs, and any credential rotation, cleanup, or replacement completed.
Related categories
Related security risks
More published guidance from the same primary category.
Trusted references
FAQ
What is affected by CVE-2026-44583?
Paymenter versions listed as affected should be reviewed: < 1.5.0.
What should I fix first?
Start with internet-facing sites, admin panels, login flows, plugins, themes, modules, packages, and systems that process user-controlled input or sensitive data.
How do I confirm the fix worked?
Apply the patched version or mitigation, clear caches where relevant, retest the affected workflow, and run a new Fixnx scan to verify public website exposure signals.
How are Fixnx security risk categories chosen?
Fixnx keeps one canonical risk page and assigns only broad, relevant categories such as ecosystem, technology area, or vulnerability class.