AI agents use snow_upload_attachment to create or update resources in Serac — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Serac environment.
This tool creates/adds a new attachment to a record, which is a reversible data modification (Write category). Severity is medium because: (1) it can accumulate unwanted files on records, potentially creating clutter or storing sensitive data in unintended places; (2) it targets a specific enterprise system (ServiceNow) where records may be business-critical; (3) however, the action is reversible (attachments can be…
From the tool's definition Tool description states 'Attach a base64-encoded file to a specific record' and 'Returns the new attachment metadata' — this creates a new attachment resource on a ServiceNow record, modifying the record's state.
Attacks that exploit this kind of access
Attach a base64-encoded file to a specific record (table_name + table_sys_id) with file name and optional MIME type. Returns the new attachment metadata. It is categorised as a Write tool in the Serac MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Serac MCP server in PolicyLayer and add a rule for snow_upload_attachment: 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 Serac. Nothing to install.
snow_upload_attachment 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 snow_upload_attachment 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 snow_upload_attachment. 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.
snow_upload_attachment is provided by the Serac MCP server (serac-labs/serac). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
snow_upload_attachment is one line of Serac's registry record.
The record carries the whole server: verified identity, auth posture, risk grade, every tool classified, recommended policy — re-checked continuously.
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