IBM Langflow SSRF Vulnerability (CVE-2026-18545)

Technical Analysis

The vulnerability likely stems from Langflow components (such as HTTP request nodes, webhook integrations, or URL-fetching tools commonly present in agent-building platforms) that accept attacker-influenced URLs without adequate validation or allowlisting. An authenticated user could craft a flow or component input causing the Langflow backend to issue requests to internal-only endpoints (e.g., cloud metadata services, internal APIs, or other services on the trusted network), bypassing network segmentation. This crosses the tool-layer boundary because the agent framework itself acts as a proxy, using its server-side privileges to reach resources the attacker could not otherwise access directly. The impact is primarily reconnaissance/enumeration, though chained with other vulnerabilities (e.g., cloud credential theft via metadata endpoints) it could escalate to more severe compromise.

Affected Systems

IBM Langflow OSS

Detection Signatures

• Outbound requests from Langflow server to unexpected internal IP ranges (e.g., 169.254.169.254, RFC1918 addresses) not tied to normal user-configured integrations
• Log entries showing URL parameters in Langflow components pointing to internal hostnames/IPs
• Repeated failed or probing requests to internal services originating from Langflow application server process
• Unusual spikes in outbound connection attempts correlated with flow execution events

Remediation Steps

1. 1

   Upgrade Langflow

   Update IBM Langflow OSS to a patched version beyond 1.11.1 once available, per vendor advisory.

2. 2

   Restrict outbound network access

   Apply network-level egress controls (firewalls, security groups) to prevent the Langflow server from reaching internal metadata services and sensitive internal hosts.

3. 3

   Validate and allowlist URLs

   If customizing or extending Langflow components, implement strict URL validation/allowlisting for any user-supplied endpoints used in HTTP-fetching nodes.

4. 4

   Enforce least-privilege authentication

   Limit which authenticated users can create or modify flows with network-request capabilities, and audit flow definitions for suspicious URL targets.

5. 5

   Monitor egress traffic

   Deploy monitoring for anomalous outbound requests from the Langflow host, especially to cloud metadata IPs or internal-only services.