CVE-2026-6618: Langgenius Dify SSRF Vulnerability

CVE-2026-6618 Overview

A Server-Side Request Forgery (SSRF) vulnerability has been discovered in Langgenius Dify, an open-source LLM application development platform. The flaw exists in the parse_openai_plugin_json_to_tool_bundle function within the api/core/tools/utils/parser.py file of the ApiBasedToolSchemaParser component. By manipulating the url argument, an attacker can force the server to make arbitrary HTTP requests to internal or external resources, potentially leading to unauthorized access to internal services, data exfiltration, or further network reconnaissance.

Critical Impact

Remote attackers with low privileges can exploit this SSRF vulnerability to access internal network resources, bypass security controls, and potentially pivot to other systems within the organization's infrastructure.

Affected Products

• Langgenius Dify versions up to 1.13.3
• ApiBasedToolSchemaParser component (api/core/tools/utils/parser.py)

Discovery Timeline

• 2026-04-20 - CVE CVE-2026-6618 published to NVD
• 2026-04-22 - Last updated in NVD database

Technical Details for CVE-2026-6618

Vulnerability Analysis

This SSRF vulnerability (CWE-918) resides in the tool schema parsing functionality of Dify's API-based tool management system. The parse_openai_plugin_json_to_tool_bundle function processes OpenAI plugin configurations and fails to properly validate or sanitize URL inputs before making server-side requests.

When a user supplies a crafted URL parameter through the affected function, the application processes it without adequate validation, allowing the server to initiate outbound requests to arbitrary destinations. This can include internal network addresses (such as 127.0.0.1, 169.254.169.254 for cloud metadata services, or private IP ranges), potentially exposing sensitive internal resources that should not be accessible from the public internet.

The attack requires network access and low-level privileges, making it exploitable by authenticated users with minimal access to the Dify platform. The vulnerability allows for limited confidentiality, integrity, and availability impacts on the vulnerable system itself.

Root Cause

The root cause of this vulnerability is insufficient input validation in the URL parsing logic within the parse_openai_plugin_json_to_tool_bundle function. The code fails to implement proper URL allowlisting, blocklisting of internal IP ranges, or DNS rebinding protections. When processing OpenAI plugin JSON configurations, the parser directly uses user-supplied URLs to fetch remote resources without verifying that the destination is an intended external endpoint.

Attack Vector

The attack is network-based and can be launched remotely by any authenticated user with access to the tool configuration features. An attacker can:

1. Access the API-based tool schema parser functionality
2. Provide a malicious URL pointing to internal resources (e.g., cloud metadata endpoints, internal APIs, or localhost services)
3. Force the server to make requests on their behalf, bypassing network segmentation
4. Exfiltrate responses containing sensitive data or use the server as a proxy for further attacks

The vulnerability mechanism involves URL parameter manipulation in the parser component. When a malicious URL is submitted, the server-side code fetches the resource without proper validation, effectively acting as an open proxy. Technical details and a proof of concept are available in the GitHub Gist PoC Resource.

Detection Methods for CVE-2026-6618

Indicators of Compromise

• Outbound HTTP requests from the Dify server to internal IP ranges (10.x.x.x, 172.16.x.x, 192.168.x.x, 127.0.0.1)
• Requests to cloud metadata endpoints such as 169.254.169.254 or metadata.google.internal
• Unusual network traffic patterns originating from the parser.py module or API tool management endpoints
• Log entries showing URL fetching activities with non-standard or internal destinations

Detection Strategies

• Monitor network egress traffic from Dify application servers for connections to internal IP ranges or cloud metadata services
• Implement application-level logging for all URL fetch operations in the api/core/tools/utils/parser.py module
• Deploy Web Application Firewall (WAF) rules to detect and block SSRF attack patterns in API requests
• Use endpoint detection and response (EDR) solutions to identify anomalous network behavior from application processes

Monitoring Recommendations

• Enable detailed logging for the ApiBasedToolSchemaParser component to capture all URL parameters processed
• Set up alerts for any server-initiated connections to RFC 1918 private address spaces or link-local addresses
• Monitor DNS queries from the application server for suspicious internal hostnames or cloud provider metadata domains
• Review audit logs for unusual tool configuration activities, particularly those involving external URL references

How to Mitigate CVE-2026-6618

Immediate Actions Required

• Restrict network access to the Dify tool configuration endpoints to trusted administrators only
• Implement network-level egress filtering to prevent the Dify server from connecting to internal resources
• Deploy WAF rules to block requests containing internal IP addresses or metadata service URLs in the url parameter
• Review existing tool configurations for any suspicious or unauthorized URL entries

Patch Information

At the time of publication, the vendor (Langgenius) has not released an official security patch for this vulnerability. According to the vulnerability disclosure, the vendor was contacted but did not respond. Organizations should monitor the Dify GitHub repository for security updates and apply patches immediately when available.

For additional technical context, refer to the VulDB Vulnerability Entry #358253 and the VulDB Submission #792241.

Workarounds

• Implement URL allowlisting at the application level to restrict allowed domains for tool configurations
• Deploy network segmentation to isolate the Dify application server from sensitive internal resources
• Use a forward proxy with strict egress rules for all outbound requests from the application
• Disable or restrict access to the ApiBasedToolSchemaParser functionality until an official patch is available

# Example iptables rules to block internal network access from the application server
# Block requests to localhost
iptables -A OUTPUT -d 127.0.0.0/8 -m owner --uid-owner dify-user -j DROP

# Block requests to private IP ranges
iptables -A OUTPUT -d 10.0.0.0/8 -m owner --uid-owner dify-user -j DROP
iptables -A OUTPUT -d 172.16.0.0/12 -m owner --uid-owner dify-user -j DROP
iptables -A OUTPUT -d 192.168.0.0/16 -m owner --uid-owner dify-user -j DROP

# Block requests to cloud metadata service
iptables -A OUTPUT -d 169.254.169.254/32 -m owner --uid-owner dify-user -j DROP