CVE-2025-56520: Dify SSRF Vulnerability in RemoteFileUploadApi

CVE-2025-56520 Overview

CVE-2025-56520 is a Server-Side Request Forgery (SSRF) vulnerability in Dify v1.6.0, an open-source large language model (LLM) application development platform. The flaw resides in the controllers.console.remote_files.RemoteFileUploadApi component, which handles remote file upload requests. An unauthenticated attacker can send crafted requests over the network to force the Dify backend to issue outbound HTTP requests to attacker-chosen destinations. The vulnerability is tracked under [CWE-918] and is distinct from CVE-2025-29720, which affected a different component in the same product.

Critical Impact
Unauthenticated remote attackers can coerce the Dify server into fetching arbitrary URLs, enabling internal network reconnaissance and access to cloud metadata services.

Affected Products

Dify v1.6.0
Component: controllers.console.remote_files.RemoteFileUploadApi
Deployments exposing the Dify console API to untrusted networks

Discovery Timeline

2025-09-30 - CVE-2025-56520 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-56520

Vulnerability Analysis

Dify exposes a remote file upload endpoint through RemoteFileUploadApi under the console controller namespace. The endpoint accepts a URL parameter and instructs the server to fetch the referenced resource so it can be ingested into the Dify pipeline. The implementation in v1.6.0 does not adequately validate or restrict the destination of these outbound requests. As a result, an attacker can supply URLs pointing to internal services, private IP ranges, loopback addresses, or cloud instance metadata endpoints such as http://169.254.169.254/. The server performs the request on behalf of the attacker and may return response content or observable side effects. This is a classic SSRF pattern in an AI application backend, where remote-fetch functionality is a common feature.

Root Cause

The root cause is missing or insufficient URL validation in the RemoteFileUploadApi controller before initiating server-side HTTP requests. Dify does not enforce an allowlist of destinations, block private and link-local address ranges, or restrict URL schemes. The vulnerability is categorized as [CWE-918] Server-Side Request Forgery.

Attack Vector

Exploitation requires only network access to the Dify console API. The attacker submits an HTTP request to the remote file upload endpoint containing a URL that resolves to an internal or otherwise sensitive resource. The Dify server processes the request and connects to the attacker-supplied destination, potentially exposing internal services, metadata credentials, or information about the internal network topology. The CVSS impact profile indicates confidentiality-only impact with no required privileges or user interaction. See the GitHub Issue Discussion for technical context.

Detection Methods for CVE-2025-56520

Indicators of Compromise

Outbound HTTP requests from the Dify backend to private RFC 1918 ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) or loopback addresses
Requests originating from Dify pods to cloud metadata endpoints such as 169.254.169.254 or metadata.google.internal
Repeated calls to /console/api/remote-files/upload from a single external source with varying URL payloads
Anomalous DNS lookups initiated by the Dify service for attacker-controlled or internal hostnames

Detection Strategies

Inspect application and proxy logs for RemoteFileUploadApi invocations containing non-public destination URLs
Deploy egress network monitoring to alert on Dify service connections to internal subnets and metadata IPs
Correlate web access logs with outbound firewall logs to identify request chaining consistent with SSRF probing

Monitoring Recommendations

Enable verbose logging of URL parameters supplied to remote file endpoints and forward logs to a centralized SIEM
Baseline normal outbound destinations for the Dify workload and alert on deviations
Monitor cloud audit logs for unexpected instance metadata service access from application workloads

How to Mitigate CVE-2025-56520

Immediate Actions Required

Upgrade Dify to a version later than v1.6.0 that addresses the RemoteFileUploadApi validation gap once a fix is available from the vendor
Restrict access to the Dify console API using network segmentation, authenticated reverse proxies, or VPN gating
Block egress traffic from the Dify service to internal networks and cloud metadata endpoints at the network layer

Patch Information

No vendor advisory or fixed version has been published in the NVD record at the time of writing. Track the upstream project through the GitHub Issue Discussion for remediation guidance and release notes.

Workarounds

Deploy an egress proxy that enforces an allowlist of external hostnames and rejects requests to private, loopback, and link-local ranges
Use Instance Metadata Service v2 (IMDSv2) on AWS and equivalent hardened metadata configurations on other cloud providers to require session tokens
Run the Dify workload in a network namespace or firewall zone that cannot reach internal management interfaces

bash

# Example iptables rules to block Dify egress to internal and metadata ranges
iptables -A OUTPUT -m owner --uid-owner dify -d 169.254.169.254 -j REJECT
iptables -A OUTPUT -m owner --uid-owner dify -d 10.0.0.0/8 -j REJECT
iptables -A OUTPUT -m owner --uid-owner dify -d 172.16.0.0/12 -j REJECT
iptables -A OUTPUT -m owner --uid-owner dify -d 192.168.0.0/16 -j REJECT
iptables -A OUTPUT -m owner --uid-owner dify -d 127.0.0.0/8 -j REJECT