CVE-2026-40933

CRITICALNVD 9.99.9—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.9 under NVD CVSS v3. EPSS exploit probability: 0.1%, top 77% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Elevated
9.9
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 2%CVSS: 9.9Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
9.9
EG Score
9.9(medium)
EPSS
78.3%
KEV
Not listed

Published

April 21, 2026

Last Modified

April 23, 2026

Advisory Details (3)

Auto-updated Jul 5, 2026
🔬 Proof of concept available. Patch available. Sources: github.
github Patch Available🟡 PoC Available

Authenticated RCE Via MCP Adapters · Advisory · FlowiseAI/Flowise · GitHub

https://github.com/FlowiseAI/Flowise/security/advisories/GHSA-c9gw-hvqq-f33r
generic

The Architectural Flaw at the Core of Anthropic's MCP

https://www.ox.security/blog/the-mother-of-all-ai-supply-chains-critical-systemic-vulnerability-at-the-core-of-the-mcp
generic

MCP STDIO Command Injection: Full Vulnerability Advisory

https://www.ox.security/blog/mcp-supply-chain-advisory-rce-vulnerabilities-across-the-ai-ecosystem

Affected Packages

(2 across 1 ecosystem)
npm(2)
PackageVulnerable rangeFixed inDependents
flowise—3.1.0—
flowise-components—3.1.0—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 8× in last 7d / 39× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 139 total refreshes for this CVE.

  1. 2026-07-11 08:27 UTCEPSS rescore
  2. 2026-07-09 19:10 UTCEPSS rescore
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  1. 2026-06-19 19:25 UTCEPSS rescore
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  7. 2026-06-15 02:46 UTCEG score recompute
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  74. 2026-06-02 16:19 UTCEG score recompute
  75. 2026-06-02 12:39 UTCEG score recompute

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Frequently asked(5)

What is CVE-2026-40933?
CVE-2026-40933 is a critical vulnerability published on April 21, 2026. 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…
When was CVE-2026-40933 disclosed?
CVE-2026-40933 was first published in the National Vulnerability Database on April 21, 2026, with the most recent update on April 23, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-40933 actively exploited?
CVE-2026-40933 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 78.3% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-40933?
CVE-2026-40933 has a CVSS v3 base score of 9.9 (NVD).
How do I remediate CVE-2026-40933?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-40933, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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