CVE-2026-56274: Flowise - Remote Code Execution via MCP Security Bypass in validateCommandFlags and validateArgsForLocalFileAccess

Severity: critical (CVSS 9.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 7.5% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-06-23 · updated 2026-06-25
Weakness: CWE-78

Description

Flowise before 3.1.2 contains multiple OS command injection vulnerabilities in the Custom MCP Server feature due to incomplete command-flag validation and a regex bypass in local file access restrictions. An attacker with a Flowise account of any role, or API access with view/update permissions for chatflows, can configure a malicious MCP server to bypass the validateCommandFlags blocklist (for example, 'docker build' is not blocked, and 'npx --yes' is not blocked while only '-y' is) and the validateArgsForLocalFileAccess checks, resulting in execution of arbitrary commands on the Flowise host.

Affected products

FlowiseAI Flowise: before 3.1.2 — fixed in 3.1.2

How to fix

Upgrade to a fixed version: FlowiseAI Flowise 3.1.2. Check the vendor advisory for mitigations.

References

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