AAP-006: Inter-Agent Semantic Message Spoofing

HASS

HERMES AGENTIC SECURITY SCORE & RISK

Target: Multi-Agent Swarms, Hierarchical Orchestrators (AutoGen, CrewAI, LangGraph)

Confidence: 96%

85 / 100

CRITICAL

Measures specific systemic risk arising from autonomy, tool authority, and cascading execution.

Dimension Breakdown

Autonomy 17 / 20

Tool Access 16 / 20

Privilege 15 / 15

Persistence 11 / 15

External Impact 13 / 15

Propagation 13 / 15

⚖️ Divergence & Operational Rationale

HASS classifies AAP-006 at 85/100 (CRITICAL). In distributed multi-agent systems, security assumptions frequently treat peer messages as trusted internal RPCs. When an adversary spoofs a supervisor directive, subordinate worker agents execute high-privilege actions without re-validating the origin or intent.

🕸️ Knowledge Graph & Related Intelligence

AAP-006: Inter-Agent Semantic Message SpoofingAGENTIC ATTACK_PATTERN

Connected Nodes: 6

Inbound Associations (Incoming)

CVE-2026-59822: LiteLLM MCP Streamable HTTP Auth BypassVULNERABILITY → enables → [This Entity]

90% VERY_HIGH

CVE-2025-54794: Claude Code Working Directory Sandbox Escape via Path Prefix MatchingVULNERABILITY → exploits → [This Entity]

92% VERY_HIGH

CVE-2026-31377: Apache Doris Frontend Meta Service Unauthenticated Access and Metadata ExfiltrationVULNERABILITY → exploits → [This Entity]

92% VERY_HIGH

CVE-2026-48746: vLLM OpenAI API Authentication Middleware Bypass via ASGI Request Handling InconsistencyVULNERABILITY → exploits → [This Entity]

92% VERY_HIGH

CVE-2026-54236: vLLM Multimodal Image Processing Unhandled Exception Memory Pointer DisclosureVULNERABILITY → exploits → [This Entity]

92% VERY_HIGH

AgentThreat StudioTOOL → evaluates → [This Entity]

99% VERY_HIGH

---

1. Architectural Mechanism: Unauthenticated Inter-Agent Channels

Hierarchical agent architectures employ an orchestrator or supervisor agent that delegates tasks to specialized worker subagents (e.g. Code Executor, SQL Runner, Shell Worker):

[Adversary injects message into message broker / shared state]
                                │
                                ▼
         ┌───────────────────────────────────────────────┐
         │ Inter-Agent Message Bus (Redis / RabbitMQ / WS)│
         └───────────────────────────────────────────────┘
                                │
                                ▼ (Unsigned Payload Accepted)
[Worker Subagent receives JSON: {"sender": "SupervisorAgent", "action": "delete_backups"}]
                                │
                                ▼ (Zero Origin Attestation)
[Worker assumes message originated from trusted orchestrator]
                                │
                                ▼
[Direct Execution of Destructive / Exfiltrating Actions]

Because most contemporary multi-agent frameworks rely on plain JSON payloads without cryptographic message signing or mutual TLS token binding, an attacker who gains access to the bus or injects text into an unvalidated conversation thread can effectively impersonate any agent in the collective.

---

2. Attack Flow Execution Chain

EXECUTION CHAIN

AAP-006: Supervisor Agent Impersonation to Worker Tool Coercion

1

Channel Eavesdropping Inter-Agent Pub/Sub Channel

Adversary gains read access to the Redis queue or websocket stream used for task distribution between agents.

2

Header & Role Spoofing Worker Subagent Message Ingress

Adversary crafts a synthetic message claiming the sender identity of the system Orchestrator with an urgent instruction.

3

Trust Exploitation Subordinate Worker Runtime

The worker agent processes the directive without authenticating the supervisor's cryptographic signature.

4

Privilege Actuation Internal Production Services

The worker agent executes privileged file deletions, API key harvesting, or remote commands on behalf of the attacker.

---

3. Detection Engineering

Sigma

title: Unsigned Inter-Agent Message Origin Mismatch
id: e124f567-8556-6fd1-fa25-4215fd500006
status: experimental
description: Detects inter-agent communication messages where the declared sender role does not match the authenticated session credentials.
author: Hermes Codex Research Team
date: 2026-09-07
logsource:
  category: application
  product: multi_agent_router
detection:
  selection:
    sender_role: "supervisor"
    auth_token_present: false
  condition: selection
fields:
  - trace_id
  - sender_role
  - recipient_agent
  - message_payload
level: high
tags:
  - attack.lateral_movement
  - attack.t1550

mTLS Message Verifier

import hmac
import hashlib
import json

def verify_inter_agent_message(
    payload: dict,
    signature: str,
    secret_key: bytes
) -> bool:
    """
    Verifies that inter-agent task delegations are signed by the authentic
    orchestrator private key before allowing worker execution.
    """
    canonical_bytes = json.dumps(payload, sort_keys=True).encode("utf-8")
    expected_sig = hmac.new(
        secret_key, canonical_bytes, hashlib.sha256
    ).hexdigest()

    if not hmac.compare_digest(signature, expected_sig):
        raise PermissionError("Inter-agent message signature verification failed. Possible spoofing attack.")
    return True

---

4. Hardened Mitigations

1. Cryptographic Message Signatures: Require all inter-agent messages to be signed with HMAC or asymmetric keys corresponding to the specific sending agent identity.
2. Independent Worker Verification: Mandate that worker agents independently evaluate whether requested actions fall within approved policy boundaries, rather than relying on blind orchestrator trust.
3. Network Isolation of Message Brokers: Bind inter-agent messaging queues strictly to localhost or private VPC subnets with mutual TLS (mTLS) enforcement.