Medium severity · published Jun 28, 2026
CVE-2026-58057
Flowise - Custom MCP Environment Variable Denylist Bypass via Case Sensitivity
5.0
CVSS
1.6%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L
Attack vector
Network
Complexity
High
Privileges
Low
User interaction
None
Confidentiality
Low
Integrity
Low
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)1.6% · higher than 75% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FL
Flowise · Flowise
before 3.1.3 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-58057
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-58057
Issue Tracking
https://github.com/FlowiseAI/Flowise/pull/6471
Exploit
https://github.com/bikini/exploitarium/tree/main/flowise-mcp-env-case-bypass-poc
Exploit
https://www.vulncheck.com/advisories/flowise-custom-mcp-environment-variable-denylist-bypass-via-case-sensitivity
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