dbcve.org
Missing AuthenticationWeakness · CWE-306

CVE-2026-5029

HIGH · 8.7 CVSS v4.0 Published 2026-05-12
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
92/100
Remediation priority · Urgent
No privileges Zero-click

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
A remote code execution vulnerability exists in Code Runner MCP Server when run with the --transport http option, which exposes the /mcp JSON-RPC endpoint without authentication on port 3088. An unauthenticated remote attacker can invoke the run-code MCP tool to supply arbitrary source code and execute it via child_process.exec() using the specified language interpreter. This allows execution of arbitrary code with the privileges of the user running the server. This vulnerability has not been fixed and might affect the project in all versions.

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

Code Runner MCP Server exposes a JSON-RPC endpoint on port 3088 without authentication when run with --transport http, allowing unauthenticated attackers to invoke the run-code tool and execute arbitrary code via child_process.exec() using the specified language interpreter.

MitigationImmediately restrict network access to the server, disable the --transport http option if not required, or implement authentication/authorization controls on the HTTP endpoint before reuse.

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
Adjacent
Complexity
Low
Privileges
None
Authentication
X
User interaction
None
Scope
X

CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

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. Identify if Code Runner MCP Server is running
    List running processes or services on the system and look for the Code Runner MCP Server process. Check process arguments, systemd service files, or startup scripts.
    Affected if The Code Runner MCP Server process is actively running on the host
  2. Verify the transport mode configuration
    Examine how the server was started by reviewing process command-line arguments, startup scripts, container run commands, or service configuration files for the --transport http flag.
    Affected if The server is running with the --transport http option enabled
  3. Confirm port 3088 is exposed
    Run netstat, ss, or nmap to check if port 3088 is listening and assess whether it is reachable from network interfaces beyond localhost.
    Affected if Port 3088 is open and accessible from non-localhost addresses
  4. Test for unauthenticated JSON-RPC access
    Send a JSON-RPC request to port 3088 with a run-code method call without providing any authentication credentials or tokens.
    Affected if The server accepts and processes JSON-RPC requests without requiring authentication

The environment is affected if Code Runner MCP Server is running with --transport http, port 3088 is network-accessible, and the endpoint accepts unauthenticated requests.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Immediately restrict network access to the server, disable the --transport http option if not required, or implement authentication/authorization controls on the HTTP endpoint before reuse.

Recommended fix High confidence
  1. Do not expose the Code Runner MCP Server --transport http endpoint to untrusted networks or the public internet
  2. Configure firewall rules (e.g., iptables, cloud security groups) to restrict access to port 3088 to only trusted IP addresses or VPN/internal networks
  3. If the HTTP transport is not required, use local transport options (e.g., stdio) which do not expose network endpoints
  4. Run the server with the principle of least privilege - use a dedicated low-privilege user account for execution
  5. Implement network-level authentication or a reverse proxy with authentication in front of the service if HTTP transport is required
  6. Monitor access logs for unexpected requests to the /mcp endpoint on port 3088

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation12.0 h
  • Testing6.0 h
  • Review / QA4.0 h
26.0 hours of engineering $4,580
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,328.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-5029 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2026-5029 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data