AI agents use upload_from_host to create or update resources in REMnux MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your REMnux MCP Server environment.
The tool uploads files from the host to the REMnux system, modifying the system's state by adding new data. This is a Write operation—reversible data modification. Severity is high because uploaded malware or malicious files could be analyzed, potentially triggering unintended tool executions if combined with analyze_file or extract_iocs.
From the tool's definition Tool name 'upload_from_host' indicates data transfer to a REMnux malware analysis system. Context shows this server executes malware analysis tools via Docker/SSH.
Documented attack patterns abuse exactly the kind of access upload_from_host gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and REMnux MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for upload_from_host:
{
"version": "1",
"default": "deny",
"tools": {
"upload_from_host": {
"limits": [
{
"counter": "upload_from_host_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}upload_from_host stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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upload_from_host. It is categorised as a Write tool in the REMnux MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the REMnux MCP Server MCP server in PolicyLayer and add a rule for upload_from_host: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches REMnux MCP Server. Nothing to install.
upload_from_host is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the upload_from_host rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for upload_from_host. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
upload_from_host is provided by the REMnux MCP Server MCP server (remnux/remnux-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 14 REMnux MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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14 REMnux MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.