{
 "public_id": "AIR-2025-0030",
 "incident_id": "2025-04-trailofbits-mcp-ansi-deception",
 "date_disclosed": "2025-04-29",
 "date_occurred": null,
 "title": "ANSI terminal escape codes hide malicious MCP tool-description payloads from users in Claude Code",
 "class": "research_demo",
 "attack_surface": "mcp_server",
 "initial_vector": "malicious_tool_description",
 "agent_capability_abused": [
  "tool_description_ingestion",
  "terminal_rendering"
 ],
 "target_product": "Claude Code 0.2.76",
 "target_vendor": "Anthropic",
 "autonomy_level": "copilot_with_approval",
 "impact_realized": false,
 "impact_type": [
  "user_deception",
  "agent_hijack"
 ],
 "blast_radius": "Terminal-based MCP clients that do not sanitize escape sequences",
 "cve": [],
 "taxonomy": {
  "owasp_asi": [
   "ASI01",
   "ASI04"
  ],
  "mitre_atlas": [],
  "labels": [
   "tool_poisoning",
   "ansi_escape",
   "ui_deception",
   "mcp"
  ]
 },
 "defense_present": null,
 "defense_bypassed": true,
 "fix_shipped": null,
 "primary_sources": [
  "https://blog.trailofbits.com/2025/04/29/deceiving-users-with-ansi-terminal-codes-in-mcp/"
 ],
 "verified_quote": "Claude does not offer any filtering or sanitization for tool descriptions and outputs containing ANSI escape sequences.",
 "confidence": "high",
 "notes": "Author Keith Hoodlet. Third post in the MCP series; no CVE assigned.",
 "risk_category": "security_fraud",
 "risk_secondary": [],
 "risk_subcategory": "Tool & Function Call Extraction / Abuse",
 "risk_sub_secondary": [],
 "ai_entity": "generative",
 "agency": "agent_acted",
 "agency_debatable": true,
 "agency_reason": "the hidden tool description hijacked the agent while deceiving the user",
 "vector_family": "malicious_component",
 "vector_detail": "malicious_tool_description",
 "guardrail_kind": [
  "unknown"
 ],
 "guardrail_outcome": "silent",
 "xrefs": {
  "aiid": [],
  "atlas": [],
  "cve": [],
  "ghsa": []
 },
 "primary_asi": "ASI01",
 "agent_framework": "unknown",
 "model_provider": "anthropic",
 "model_name": "",
 "detection_mechanism": "external_researcher",
 "tool_access": "unknown",
 "financial_loss_band": "unknown",
 "eai_category": "supply_chain_vulnerabilities",
 "eai_domain": "tool_misuse",
 "eai_secondary": [
  "human_manipulation"
 ],
 "eai_reason": "impact rule: supply_chain_vulnerabilities",
 "asi_curated": [
  "ASI01"
 ],
 "asi_scope": "in_scope",
 "asi_provenance": "curated_plus_rule",
 "asi_reason": "curated: ASI01 | added ASI04 (vector_family=malicious_component)",
 "submitted_by": "EAI Internal"
}