CVE-2025-59527: Flowiseai Flowise SSRF Vulnerability

CVE-2025-59527 Overview

A Server-Side Request Forgery (SSRF) vulnerability has been identified in Flowise, the popular drag-and-drop user interface for building customized large language model (LLM) flows. The vulnerability exists in the /api/v1/fetch-links endpoint of the Flowise application, allowing attackers to leverage the Flowise server as a proxy to access internal network web services and explore their link structures. This flaw poses significant risks to organizations using Flowise in environments with access to sensitive internal resources.

Critical Impact

Attackers can exploit this SSRF vulnerability to probe internal network infrastructure, access internal web services, and potentially exfiltrate sensitive information from resources that should not be publicly accessible.

Affected Products

• FlowiseAI Flowise version 3.0.5
• Organizations running unpatched Flowise instances with network access to internal services
• LLM workflow deployments exposed to untrusted users or the internet

Discovery Timeline

• 2025-09-22 - CVE-2025-59527 published to NVD
• 2025-09-23 - Last updated in NVD database

Technical Details for CVE-2025-59527

Vulnerability Analysis

This Server-Side Request Forgery (SSRF) vulnerability (CWE-918) affects the /api/v1/fetch-links endpoint in Flowise version 3.0.5. The endpoint is designed to fetch and parse links from external URLs, but lacks proper validation of the target URL parameter. This design flaw allows an attacker to supply arbitrary URLs, including those pointing to internal network resources, effectively using the Flowise server as an unwitting proxy.

The vulnerability is exploitable remotely without authentication, making it particularly dangerous in deployments where the Flowise instance has network connectivity to sensitive internal systems. An attacker can craft malicious requests to scan internal IP ranges, access cloud metadata endpoints, or retrieve data from internal web applications that would otherwise be inaccessible from external networks.

Root Cause

The root cause of this vulnerability lies in insufficient URL validation within the fetch-links functionality. The fetch links controller and fetch links service modules accept user-supplied URLs and process them without restricting requests to internal IP addresses, localhost, or cloud metadata services. The utility code responsible for URL handling does not implement allowlisting or blocklisting mechanisms to prevent SSRF attacks.

Attack Vector

The vulnerability is network-accessible, requiring no user interaction or authentication to exploit. An attacker sends a crafted HTTP request to the /api/v1/fetch-links endpoint with a URL parameter pointing to an internal resource. The Flowise server then makes a request to the specified URL on behalf of the attacker and returns the response, effectively bypassing network segmentation and firewall controls.

Potential attack scenarios include:

• Accessing cloud provider metadata endpoints (e.g., http://169.254.169.254/) to retrieve IAM credentials
• Scanning internal IP ranges to map network topology and discover services
• Retrieving configuration files or sensitive data from internal web applications
• Bypassing VPN or firewall restrictions by pivoting through the Flowise server

Detection Methods for CVE-2025-59527

Indicators of Compromise

• Unusual outbound requests from the Flowise server to internal IP ranges (e.g., 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16)
• Requests to cloud metadata endpoints (169.254.169.254) originating from the Flowise application
• High volume of requests to the /api/v1/fetch-links endpoint from a single source
• Error logs indicating failed connections to unexpected internal hosts

Detection Strategies

• Monitor HTTP access logs for the /api/v1/fetch-links endpoint and flag requests containing internal IP addresses or reserved hostnames
• Implement network-level monitoring to detect outbound connections from the Flowise server to internal services it should not access
• Configure web application firewalls (WAF) to inspect and block SSRF payloads targeting the vulnerable endpoint
• Enable verbose logging on the Flowise application to capture all URL fetch attempts for forensic analysis

Monitoring Recommendations

• Set up alerts for any Flowise server connections to RFC 1918 private IP ranges or link-local addresses
• Implement egress filtering rules and log violations to identify potential SSRF exploitation attempts
• Regularly audit Flowise access logs for anomalous patterns in the fetch-links endpoint usage
• Deploy network detection rules to identify SSRF patterns in HTTP traffic

How to Mitigate CVE-2025-59527

Immediate Actions Required

• Upgrade Flowise to version 3.0.6 or later immediately, as this version contains the security patch
• If immediate patching is not possible, restrict network access to the Flowise server from untrusted sources
• Implement network segmentation to limit the Flowise server's access to sensitive internal resources
• Review access logs for any signs of prior exploitation

Patch Information

FlowiseAI has addressed this vulnerability in version 3.0.6. Organizations should upgrade to this version or later to remediate the SSRF vulnerability. The patch implements proper URL validation to prevent requests to internal network resources. For complete details, refer to the FlowiseAI Security Advisory GHSA-hr92-4q35-4j3m.

Workarounds

• Deploy a reverse proxy or web application firewall (WAF) in front of Flowise to filter requests containing internal IP addresses or dangerous URL schemes
• Implement network-level egress filtering to prevent the Flowise server from connecting to internal IP ranges
• Restrict access to the /api/v1/fetch-links endpoint to trusted users only via authentication and authorization controls
• Consider running Flowise in an isolated network segment with no connectivity to sensitive internal resources

# Example: Block internal network access using iptables (Linux)
# Prevent Flowise from accessing internal networks
iptables -A OUTPUT -m owner --uid-owner flowise -d 10.0.0.0/8 -j DROP
iptables -A OUTPUT -m owner --uid-owner flowise -d 172.16.0.0/12 -j DROP
iptables -A OUTPUT -m owner --uid-owner flowise -d 192.168.0.0/16 -j DROP
iptables -A OUTPUT -m owner --uid-owner flowise -d 169.254.169.254 -j DROP