CVE-2026-33309: Langflow

Critical severity, CVSS 9.9. EPSS: 1% chance of exploitation in the next 30 days.

Langflow is a tool for building and deploying AI-powered agents and workflows. Versions 1.2.0 through 1.8.1 have a bypass of the patch for CVE-2025-68478 (External Control of File Name), leading to the root architectural issue within `LocalStorageService` remaining unresolved. Because the underlying storage layer lacks boundary containment checks, the system relies entirely on the HTTP-layer `ValidatedFileName` dependency. This defense-in-depth failure leaves the `POST /api/v2/files/` endpoint vulnerable to Arbitrary File Write. The multipart upload filename bypasses the path-parameter guard, allowing authenticated attackers to write files anywhere on the host system, leading to Remote Code Execution (RCE). Version 1.9.0 contains an updated fix.

Affected products

• Langflow Langflow: from 1.2.0, before 1.9.0 (fixed in 1.9.0)

Published 2026-03-24. Last modified 2026-06-17.