CVE-2026-33309 Langflow has an Arbitrary File Write (RCE) via v2 API
Authenticated attackers can bypass file name validation to write arbitrary files on the host, leading to remote code execution in Langflow.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-33309?
CVE-2026-33309 is a critical path traversal vulnerability in Langflow Langflow, published on 24 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-33309?
3 open source packages ship an affected version, including langflow. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
langflow PyPI | From 1.2.0 | 1.9.0 |
langflow PyPI | From 1.2.0 | 1.9.0 |
langflow PyPI | From 1.2.0 | 1.9.0 |
Products include Langflow Langflow.
How do I fix CVE-2026-33309?
Upgrade langflow to 1.9.0 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-33309 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-33309 exists.
Other vulnerabilities in Langflow Langflow
Sources
Also known as ECHO-6551-da8d-a4b8, GHSA-g2j9-7rj2-gm6c, PYSEC-2026-79.