# CVE-2026-55446: Langflow unauthenticated denial of service in file upload

Source: https://junglewise.ai/threats/cve-2026-55446-langflow-unauthenticated-denial-of-service-in-file-upload  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-23. Updated: 2026-06-23  
License: CC BY 4.0 with a link back

CVE-2026-55446 · Severity: high · CVSS 7.5 · Published 2026-06-23

Langflow, a tool for building AI workflows, is vulnerable to a denial-of-service attack that can take the entire application offline. An attacker can send a specially crafted file upload request that forces the server to consume excessive resources, making it unresponsive to all users. This attack does not require a password or any special access, potentially leading to indefinite service outages.

Technologies: [langflow (PyPI)](https://junglewise.ai/threats/technologies/pypi-langflow). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-55446 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-55446 being exploited in the wild.

**How severe is CVE-2026-55446?** High severity, with a CVSS score of 7.5, published 23 June 2026.

**Which products and versions are affected?** langflow (PyPI) ECOSYSTEM:introduced=0,fixed=1.0.19.

**Is there a fix for CVE-2026-55446?** Yes. langflow (PyPI): upgrade to 1.0.19 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-55446 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-55446?** Check whether you run langflow (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- langflow (PyPI): upgrade to 1.0.19 or later

  ```sh
  pip install "langflow>=1.0.19"
  ```


## Technical details

A vulnerability in Langflow's file upload endpoint (/api/v1/files/upload/) allows for unauthenticated denial-of-service via uncontrolled resource consumption (CWE-400). The application fails to validate the multipart form boundary before processing, allowing an attacker to submit a payload containing an extremely large number of hyphens (e.g., 1,000,000+) following the boundary. This causes the server to enter a 'busy' state indefinitely while attempting to parse the malformed data. Additionally, the endpoint lacked authentication checks, allowing remote, unauthenticated attackers to trigger the flaw. Version 1.0.19 fixes this by implementing a 'check_boundary' middleware to validate boundary length and format, and by enforcing authentication and flow-ownership checks.

## Affected products

- langflow-ai Langflow < 1.0.19

## Identifiers

- CVE-2026-55446
- GHSA-qwqc-p3q8-wcg9
- PYSEC-2026-223

## Timeline

- 2024-09-30: patched: Fix merged in pull request #3923
- 2026-06-19: advisory: GitHub Security Advisory published
- 2026-06-23: disclosed: CVE-2026-55446 published to NVD

## References

- [https://github.com/langflow-ai/langflow/pull/3923](https://github.com/langflow-ai/langflow/pull/3923)
- [https://github.com/langflow-ai/langflow/security/advisories/GHSA-qwqc-p3q8-wcg9](https://github.com/langflow-ai/langflow/security/advisories/GHSA-qwqc-p3q8-wcg9)

## Related threats

- [Langflow SSRF in URL-taking components](https://junglewise.ai/threats/langflow-ssrf-in-url-taking-components-protection-disabled-by-default-db7cac37)
- [Langflow IP spoofing in MCP configuration installation](https://junglewise.ai/threats/cve-2026-105741-langflow-is-a-tool-for-building-and-deploying-ai-powered-agents)
- [Langflow path traversal and cross-user disclosure in MCP resources](https://junglewise.ai/threats/cve-2026-105699-langflow-is-a-tool-for-building-and-deploying-ai-powered-agents)
- [Langflow authorization bypass in flow API endpoints](https://junglewise.ai/threats/cve-2026-105698-langflow-is-a-tool-for-building-and-deploying-ai-powered-agents)
- [Langflow MCP stdio command injection](https://junglewise.ai/threats/cve-2026-105697-langflow-is-a-tool-for-building-and-deploying-ai-powered-agents)