---
title: "CVE-2026-33309: Langflow has an Arbitrary File Write (RCE) via v2 API"
url: https://erroneo.us/security/cve/CVE-2026-33309/
description: "CVE-2026-33309 (langflow (PyPI)): Langflow is a tool for building and deploying AI-powered agents and workflows. Versions 1.2.0 through 1.8.1 have a bypass…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-03-24
date_modified: 2026-06-06
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-33309"
kev: false
cvss: 10
epss: 0.01089
license: All rights reserved. Quote with attribution and a link.
---

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

**Signal:** Critical, preconditions apply. Severe if exploited, but exploitation needs conditions that may not apply to you. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 1.1% , percentile 65: FIRST’s model estimates a 1.1% chance of exploitation activity in the next 30 days, higher than 65% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Needs an account (low (any account)). Exposure depends on who can log in.
- Only applies if your dependency tree includes langflow (PyPI) >= 1.2.0, < 1.9.0, fixed in 1.9.0 . Check your lockfile, including transitive dependencies.

## What it is

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 packages

- PyPI `langflow` >= 1.2.0, < 1.9.0 → fixed: 1.9.0

## Affected products (CVE record)

- langflow-ai langflow: >= 1.2.0, < 1.9.0

## Severity

- GitHub_M CVSS 3.1: 10 `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H`
- GitHub CVSS 3.1: 9.9 `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable no , technical impact total .
- FIRST EPSS (model of 2026-10-21): 1.09% probability of exploitation activity in the next 30 days; percentile 65.

## Sources

- [GitHub Advisory GHSA-g2j9-7rj2-gm6c](https://github.com/advisories/GHSA-g2j9-7rj2-gm6c)
- [CVE.org record CVE-2026-33309](https://www.cve.org/CVERecord?id=CVE-2026-33309)
- [NVD entry CVE-2026-33309](https://nvd.nist.gov/vuln/detail/CVE-2026-33309)
- [github.com](https://github.com/langflow-ai/langflow/security/advisories/GHSA-g2j9-7rj2-gm6c)
- [github.com](https://github.com/pypa/advisory-database/tree/main/vulns/langflow/PYSEC-2026-79.yaml)

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Source page: https://erroneo.us/security/cve/CVE-2026-33309/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt