IBM Langflow Path Traversal Arbitrary File Read (CVE-2026-18899)

Technical Analysis

The vulnerability stems from insufficient sanitization of file path input in one or more Langflow endpoints, likely those handling file uploads, flow imports, or static asset retrieval, allowing directory traversal sequences to escape the intended base directory. A remote attacker with network access to the Langflow instance can exploit this without needing to compromise any AI logic, agent prompt, or tool definition. Successful exploitation grants read access to arbitrary files on the server's filesystem, which in an agent-hosting environment may include API keys, environment variables, database credentials, or serialized agent state and conversation logs. This crosses a boundary from the web application layer into the underlying host, potentially enabling further lateral movement or secondary compromise of connected agents and tools that rely on the same credentials.

Affected Systems

Langflow

Detection Signatures

• HTTP requests to Langflow file/flow/asset endpoints containing encoded or literal directory traversal sequences (e.g., '../', '%2e%2e%2f') in path or filename parameters
• Unexpected 200 responses returning file contents outside expected upload/flow directories
• Access logs showing repeated probing of static file or import endpoints from unauthenticated or unexpected source IPs
• File access to sensitive paths (e.g., /etc/passwd, .env, credentials files) triggered via web application process rather than normal admin tooling

Remediation Steps

1. 1

   Upgrade Langflow

   Update to a patched Langflow release beyond 1.11.1 that fixes the path traversal issue as soon as it is available from IBM/Langflow maintainers.

2. 2

   Restrict network exposure

   Ensure Langflow instances are not directly exposed to the public internet; place them behind authentication, VPN, or a reverse proxy with strict access controls.

3. 3

   Input validation and sandboxing

   Apply WAF rules to detect and block path traversal patterns in requests, and run Langflow with a restricted filesystem/container sandbox limiting readable paths.

4. 4

   Credential rotation

   Rotate any API keys, secrets, or credentials stored on or accessible from the Langflow host in case they were exposed prior to patching.

5. 5

   Audit logs

   Review historical access logs for suspicious traversal patterns to determine if exploitation already occurred and scope any resulting exposure.