CVE-2026-55255: Langflow Authorization Bypass Through User-Controlled Key Vulnerability

Severity: high (CVSS 8.4 v3.1)
Exploited in the wild: yes — in CISA KEV since 2026-07-07
EPSS: 0.9% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-06-23 · updated 2026-10-25
Weakness: CWE-639

Description

Langflow is a tool for building and deploying AI-powered agents and workflows. Prior to 1.9.1, an Insecure Direct Object Reference (IDOR) vulnerability in /api/v1/responses endpoint allows an authenticated attacker to execute any flow belonging to another user by specifying the victim's flow ID in the request. This vulnerability is fixed in 1.9.1.

Affected products

IBM Langflow OSS: before 1.9.1 — fixed in 1.9.1

How to fix

Upgrade to a fixed version: IBM Langflow OSS 1.9.1. Check the vendor advisory for mitigations.

References

https://github.com/langflow-ai/langflow/commit/2c9f498d664a3c32698b57d7c5e752625291060e
https://github.com/langflow-ai/langflow/pull/12832
https://github.com/langflow-ai/langflow/security/advisories/GHSA-qrpv-q767-xqq2
https://github.com/langflow-ai/langflow/security/advisories/GHSA-qrpv-q767-xqq2
https://webflow.sysdig.com/blog/understanding-langflow-cve-2026-55255-and-why-higher-cvss-vulnerabilities-arent-always-the-most-exploited
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-55255

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