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Code InjectionWeakness · CWE-94

CVE-2026-30618

CRITICAL · 9.8 CVSS v3.1 Published 2026-07-15
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click 5 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
xszyou Fay 4.3.1 contains a remote code execution vulnerability in its MCP STDIO server management and command execution handling. A remote attacker can access the publicly exposed MCP management interface and configure an MCP STDIO server with attacker-controlled commands and parameters, resulting in execution of arbitrary commands on the server. Successful exploitation allows arbitrary command execution within the context of the Fay service.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The vulnerability exists in the MCP STDIO server management component of xszyou Fay 4.3.1. The MCP management interface is publicly exposed without proper access controls, allowing remote attackers to configure MCP STDIO servers with attacker-supplied commands and parameters. This results in arbitrary command execution within the context of the Fay service.

MitigationImmediately restrict network access to the MCP management interface by implementing authentication, IP allowlisting, or network segmentation to prevent unauthorized access. Review and validate all command parameters accepted by the MCP STDIO server configuration.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Verify Fay service version
    Check the installed version of xszyou Fay service (e.g., via software inventory, service banner, or version file). Compare against the affected version 4.3.1.
    Affected if Running version 4.3.1 of xszyou Fay
  2. Identify MCP management interface exposure
    Scan network listeners or firewall rules to determine if the MCP STDIO server management port/endpoint is accessible from untrusted networks (e.g., Internet or external VLANs).
    Affected if MCP management interface listens on a publicly reachable network address without authentication barriers
  3. Check MCP configuration for access controls
    Inspect the Fay service configuration files or management interface settings to verify whether authentication, IP allowlisting, or other access controls are enabled for the MCP component.
    Affected if No authentication or access control mechanisms are configured for the MCP management interface
  4. Inspect MCP STDIO server definitions
    Review the MCP STDIO server configuration (e.g., configuration files, database records, or runtime settings) to identify if any server definitions accept external command parameters.
    Affected if MCP STDIO servers are configured to accept arbitrary or attacker-controlled commands and parameters
  5. Audit network connectivity to MCP port
    Use netstat, ss, or similar tools to list all listening ports associated with the Fay service, then verify if the MCP management port accepts connections from untrusted sources.
    Affected if The MCP management port accepts connections from any IP address (0.0.0.0 or unrestricted binding)

A user is affected if running xszyou Fay version 4.3.1 with the MCP STDIO server management interface exposed to untrusted networks without access controls, allowing arbitrary command configuration.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Immediately restrict network access to the MCP management interface by implementing authentication, IP allowlisting, or network segmentation to prevent unauthorized access. Review and validate all command parameters accepted by the MCP STDIO server configuration.

Have this fixed Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-30618 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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