Substitute the service name in a service ticket. Replaces the SPN in an existing TGS with a different service name. Useful when you have a ticket for one service but need access to another on the same server (requires same service account).
AI agents invoke rubeus_tgssub to trigger actions in Rubeus MCP Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.
This tool manipulates Kerberos service tickets to substitute SPNs, enabling unauthorized lateral access to services beyond what was originally granted. It is a Kerberos abuse operation (as stated in the server description) that actively executes ticket manipulation — a privilege escalation/lateral movement technique.
From the tool's definition Substitute the service name in a service ticket. Replaces the SPN in an existing TGS with a different service name. Useful when you have a ticket for one service but need access to another on the same server (requires same service account).
Attacks that exploit this kind of access
Substitute the service name in a service ticket. Replaces the SPN in an existing TGS with a different service name. Useful when you have a ticket for one service but need access to another on the same server (requires same service account). It is categorised as a Execute tool in the Rubeus MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Rubeus MCP Server MCP server in PolicyLayer and add a rule for rubeus_tgssub: 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 Rubeus MCP Server. Nothing to install.
rubeus_tgssub is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the rubeus_tgssub 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 rubeus_tgssub. 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.
rubeus_tgssub is provided by the Rubeus MCP Server MCP server (schwarztim/sec-rubeus-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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