Vulnerability · Published Jun 28, 2026 · Assigned by VulnCheck

CVE-2026-58057Flowise - Custom MCP Environment Variable Denylist Bypass via Case Sensitivity

Medium 5.0

In plain English

A medium-severity security flaw in Flowise from Flowise. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 1.6% (higher than 75% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code.

Severity (CVSS 3.1)5.0Medium

Exploit odds (30 days)1.6%top 24.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack tooling1Public PoC

Official description

Flowise before 3.1.3 validates Custom MCP stdio environment variables against a denylist using a case-sensitive comparison, so on Windows, where environment names are case-insensitive, supplying 'node_options' bypasses the NODE_OPTIONS denylist entry. An authenticated user who can configure a Custom MCP node can thereby inject NODE_OPTIONS --require and execute arbitrary code in the Flowise server context.

Affected products (as reported)

Vendor	Product	Versions
Flowise	Flowise	0 – before 3.1.3

Weakness: CWE-178 · Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L

References

Proof of Concept exploit, third-party-advisory
Fix (PR #6471, 3.1.3) issue-tracking
VulnCheck Advisory: Flowise - Custom MCP Environment Variable Denylist Bypass via Case Sensitivity third-party-advisory