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

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-06-23 · updated 2026-10-25
Weakness: CWE-400

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.

Affected products

IBM Langflow OSS: before 1.0.19 — fixed in 1.0.19

How to fix

Upgrade to a fixed version: IBM Langflow OSS 1.0.19. Check the vendor advisory for mitigations.

References

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

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