CVE-2026-91931 FlowiseAI CVE debrief

Who should care

Defenders responsible for Flowise server configurations and security should assess exposure and prioritize upgrading to version 3.1.4 or later. This includes operators, security teams, and vulnerability management teams who need to verify the vulnerability and implement remediation measures.

Why it matters

CVE-2026-91931 is a critical remote code execution vulnerability in Flowise before 3.1.4 that allows authenticated attackers to execute arbitrary code. Defenders responsible for Flowise server configurations and security should assess exposure and prioritize upgrading to version 3.1.4 or later.

• Authenticated attackers can execute arbitrary code on the Flowise server.
• Flowise server configurations need to be verified to ensure the Custom MCP node is not vulnerable.
• Upgrading to version 3.1.4 or later is necessary to remediate the vulnerability.

Technical summary

Flowise before 3.1.4 contains a remote code execution vulnerability in the Custom MCP node that allows authenticated attackers to execute arbitrary code by supplying npx package names in the mcpServerConfig parameter. The vulnerability has a CVSS score of 9 and a severity of CRITICAL. The vulnerability is caused by a lack of proper validation of user input in the Custom MCP node, which allows authenticated attackers to execute arbitrary code. The affected versions are Flowise before 3.1.4, and the recommended remediation is to upgrade to version 3.1.4 or later.

Defensive priority

Defenders should prioritize verifying Flowise server configurations and upgrading to version 3.1.4 or later.

Recommended defensive actions

• Verify Flowise server configurations to ensure the Custom MCP node is not vulnerable.
• Upgrade Flowise to version 3.1.4 or later.
• Monitor Flowise server logs for suspicious activity.
• Review compensating controls for exposed systems while remediation is scheduled and verified.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.

Evidence notes

The CVE record and NVD entry provide details on the remote code execution vulnerability in Flowise before 3.1.4. The vulnerability is caused by a lack of proper validation of user input in the Custom MCP node, which allows authenticated attackers to execute arbitrary code. The CVE record and NVD entry also provide information on the affected versions and the recommended remediation.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.