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CVE-2025-6514 is a critical remote code execution vulnerability affecting the mcp-remote package, specifically impacting versions 0.0.5 through 0.1.15.
The flaw manifests during the initial connection handshake and authorization exchange between an AI client and a remote Model Context Protocol server.
When a developer or user configures an LLM client such as Claude Desktop to link with an external MCP server, mcp-remote manages the underlying network stream.
During this protocol negotiation phase, a malicious or compromised remote server can transmit specially crafted command payloads disguised as server configuration data.
Because the vulnerable versions lack proper sanitization and validation checks on incoming handshake parameters, the client script interprets the payload instructions insecurely.
Instead of safely parsing the data as text tokens, the execution flow passes the strings directly to the underlying host operating system shell.
This arbitrary command execution occurs immediately upon connection, operating entirely under the security context and permissions of the user running the local LLM client.
Because AI clients frequently operate with broad user privileges to read workspace files and execute terminal tools, the exploit achieves high-impact host compromise without requiring prior authentication.
Adversaries leverage this by hosting rogue MCP servers that wait for client connections, instantly replying with shell scripts during the initial protocol greeting.
The vulnerability bypasses traditional web application firewalls because traffic flows over legitimate MCP transport protocols like Server-Sent Events or standard stdio wrappers.
Security researchers identified this vector while auditing the trust boundaries established between modern AI agents and external tool providers.
Mitigating the issue requires immediate package upgrades and strict server allowlisting to ensure clients only communicate with verified, trusted infrastructure endpoints.
DailyCVE Form:
Platform: mcp-remote client tool
Version: 0.0.5 to 0.1.15
Vulnerability : Remote Code Execution
Severity: Critical Risk Score
date: Early 2025 release
Prediction: Patched in 0.1.16
(end of form)
What Undercode Say:
Analytics indicate that protocol-level integrations in AI agent ecosystems introduce unique attack surfaces where trust is implicitly granted to server responses. The prevalence of mcp-remote across developer setups magnified systemic risk, turning standard LLM workflows into vectors for host compromise. Security telemetry highlights that supply chain dependencies in AI tooling require rigorous input validation during handshake phases, as protocol parsing bugs bypass conventional web application controls.
Exploit: (Educational Purposes!)
Check installed vulnerable version of mcp-remote package
npm list mcp-remote
Example configuration snippet demonstrating vulnerable remote server binding
cat << 'EOF' > vulnerable_config.json
{
"mcpServers": {
"untrusted-remote": {
"command": "npx",
"args": ["mcp-remote", "https://malicious-server-endpoint.example/sse"]
}
}
}
EOF
Simulating connection check log inspection for unauthorized command triggers
tail -n 50 ~/.npm/_logs/_debug.log | grep -i "mcp-remote"
Protection: from this CVE
Upgrade the mcp-remote package immediately to version 0.1.16 or later where input sanitization during handshakes is enforced. Restrict client configurations exclusively to trusted, internally hosted or authenticated MCP servers. Implement egress network filtering on developer endpoints to prevent unauthorized outbound connections to untrusted remote server ports.
Impact:
Successful exploitation allows unauthenticated remote attackers to execute arbitrary operating system commands on the victim’s local machine. Because LLM clients often possess broad permissions, this leads to immediate local privilege abuse, theft of sensitive environment variables, data exfiltration from project directories, and potential full host takeover.
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Sources:
Reported By: github.com
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