RCE in Flowiseai Flowise
CVE-2026-40933
Flowise is a drag & drop user interface to build a customized large language model flow. Prior to 3.1.0, due to unsafe serialization of stdio commands in the MCP adapter, an authenticated attacker can add an MCP stdio server with an arbitrary command, achieving command execution. The vulnerability lies in a bug in the input sanitization from the “Custom MCP” configuration in http://localhost:3000/canvas - where any user can add a new MCP, when doing so - adding a new MCP using stdio, the user can add any command, even though your code have input sanitization checks such as validateCommandInjection and validateArgsForLocalFileAccess, and a list of predefined specific safe commands - these commands, for example "npx" can be combined with code execution arguments ("-c touch /tmp/pwn") that enable direct code execution on the underlying OS. This vulnerability is fixed in 3.1.0.
Vulnerability class: Command Injection (OS Command Injection)
EPSS: 0.134 (96.1th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 9.9 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H.
Affected products
- Flowiseai Flowise — versions < 3.1.0
- Flowiseai Flowise-components — versions < 3.1.0
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Vendor Advisory)
- security-advisories@github.com (Third Party Advisory, x_refsource_MISC, Press/Media Coverage)
- security-advisories@github.com (Third Party Advisory, x_refsource_MISC, Press/Media Coverage)
Frequently asked questions
- What is CVE-2026-40933?
- CVE-2026-40933 is a critical-severity vulnerability in Flowiseai Flowise, classified under OS Command Injection. CVSS score: 9.9/10. Published 2026-04-21.
- How severe is CVE-2026-40933?
- Critical severity. CVSS v3 base score is 9.9 out of 10.