CVE-2026-4623: Jeson CRM System SSRF Vulnerability

CVE-2026-4623 Overview

A Server-Side Request Forgery (SSRF) vulnerability has been identified in DefaultFuction Jeson-Customer-Relationship-Management-System. This vulnerability affects the /api/System.php file within the API Module component, where improper handling of the url parameter allows attackers to manipulate server-side requests. An unauthenticated remote attacker can exploit this flaw to force the server to make arbitrary HTTP requests to internal or external resources, potentially leading to data exfiltration, internal network reconnaissance, or access to sensitive internal services.

Critical Impact

Remote attackers can exploit this SSRF vulnerability to access internal services, scan internal networks, and potentially pivot to other systems within the network infrastructure.

Affected Products

• DefaultFuction Jeson-Customer-Relationship-Management-System (versions up to commit 1b4679c4d06b90d31dd521c2b000bfdec5a36e00)

Discovery Timeline

• 2026-03-24 - CVE-2026-4623 published to NVD
• 2026-03-24 - Last updated in NVD database

Technical Details for CVE-2026-4623

Vulnerability Analysis

This SSRF vulnerability exists in the external_api case handler within /api/System.php. The application accepts a user-controlled url parameter via GET request and passes it directly to a cURL function without proper validation or sanitization. This allows attackers to specify arbitrary URLs, causing the server to make requests on behalf of the attacker. The vulnerability can be exploited to access internal services that would otherwise be unreachable from external networks, including cloud metadata endpoints, internal APIs, and administrative interfaces.

Root Cause

The root cause stems from insufficient input validation on the url parameter in the external_api endpoint. The application directly uses user-supplied input in the sendCurlRequest() function without implementing URL allowlisting, protocol restrictions, or proper sanitization. This design flaw allows attackers to redirect server-side requests to arbitrary destinations, including internal network resources and localhost services.

Attack Vector

The vulnerability is exploitable remotely via the network without authentication. An attacker can craft malicious requests to the /api/System.php endpoint with the url parameter pointing to internal services such as http://127.0.0.1:8080/admin or cloud metadata endpoints like http://169.254.169.254/latest/meta-data/. The server will execute the request and return the response, effectively bypassing network security controls and exposing internal resources to the attacker.

     case 'external_api':
-        ##$url = $_GET['url'] ?? 'https://api.example.com/data';
+        $url = $_GET['url'] ?? 'https://api.example.com/data';
         $response = sendCurlRequest($url);
         echo json_encode(['data' => $response]);
         break;

Source: GitHub Commit Details

Detection Methods for CVE-2026-4623

Indicators of Compromise

• Unusual outbound requests from the web server to internal IP ranges (e.g., 10.x.x.x, 172.16.x.x, 192.168.x.x, 127.0.0.1)
• HTTP requests to cloud metadata endpoints (169.254.169.254) originating from the application server
• Unexpected access patterns to /api/System.php with suspicious url parameter values
• Server-side requests to ports commonly associated with internal services (22, 3306, 6379, 8080, etc.)

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block SSRF patterns in the url parameter
• Monitor server egress traffic for connections to internal network ranges or localhost addresses
• Deploy network intrusion detection systems (NIDS) to identify anomalous server-initiated requests
• Review application logs for requests to /api/System.php containing IP addresses or internal hostnames

Monitoring Recommendations

• Enable detailed logging for all requests to the /api/System.php endpoint, including full query parameters
• Configure alerts for server-side requests to RFC 1918 private IP address ranges
• Monitor for access attempts to common cloud metadata endpoints from application servers
• Implement network segmentation monitoring to detect lateral movement attempts via SSRF

How to Mitigate CVE-2026-4623

Immediate Actions Required

• Apply the security patch identified by commit f76e7123fe093b8675f88ec8f71725b0dd186310 or 98bd4eb07fa19d4f2c5228de6395580013c97476
• Implement URL allowlisting for the external_api functionality to restrict requests to approved domains only
• Deploy a web application firewall with SSRF detection rules in front of the application
• Restrict outbound network access from the web server to only necessary external services

Patch Information

A security patch has been released by the maintainers. The fix is available in commits f76e7123fe093b8675f88ec8f71725b0dd186310 and 98bd4eb07fa19d4f2c5228de6395580013c97476. Since this product uses continuous delivery with rolling releases, users should pull the latest version from the GitHub Project Repository. Additional details are available in the GitHub Issue Tracker and VulDB Threat Report.

Workarounds

• Disable or restrict access to the external_api endpoint until the patch can be applied
• Implement network-level egress filtering to block requests to internal IP ranges from the web server
• Use a reverse proxy to intercept and validate all outbound requests from the application
• Apply IP-based access controls to limit who can reach the /api/System.php endpoint

# Example: Block internal IP ranges in iptables for outbound traffic from web server
iptables -A OUTPUT -m owner --uid-owner www-data -d 10.0.0.0/8 -j DROP
iptables -A OUTPUT -m owner --uid-owner www-data -d 172.16.0.0/12 -j DROP
iptables -A OUTPUT -m owner --uid-owner www-data -d 192.168.0.0/16 -j DROP
iptables -A OUTPUT -m owner --uid-owner www-data -d 127.0.0.0/8 -j DROP
iptables -A OUTPUT -m owner --uid-owner www-data -d 169.254.169.254 -j DROP