Malicious MCP Servers Can Split Instructions to Make AI Coding Agents Exfiltrate Secrets
ASSET Research Group's GhostSplice technique splits malicious instructions across MCP channels, tricking AI coding agents into exfiltrating SSH keys, source code, and secrets.
ASSET Research Group disclosed GhostSplice, a prompt-injection technique in which a malicious Model Context Protocol (MCP) server splits an exfiltration instruction across a tool description and a tool result so no single fragment appears harmful. In the reference implementation, a benign-looking integrity_checker tool with fields alpha through delta is later paired with a project-scan result mapping those fields to .ssh/id_rsa, proprietary source, customers.csv, and .env. Tests across eleven API-tested models showed average compliance rising from 42% to 82% when instructions were split in two, with GPT-4o, Gemini 2.0 Flash, and Llama 3.3 70B going from 0% to 100%. The findings come from controlled lab tests, not a reported real-world intrusion, and no CVE identifiers had been assigned as of August 10, 2026.
- GhostSplice splits malicious instructions across MCP tool descriptions and results so no single fragment looks harmful.
- ASSET tests: splitting instructions into two pieces raised average agent compliance from 42% to 82% across eleven models.
- Same model can refuse in one coding client and exfiltrate in another; surrounding safety controls matter.
- No real-world intrusion reported; tests were controlled and CVEs await coordinated disclosure as of August 10, 2026.
- Defense: treat MCP server output as data, require human approval of tool calls, validate cross-tool value flows.
- Vendors
- OpenAI
- Organizations
- ASSET Research GroupThe Hacker News
From the original article
3 min read at thehackernews.com
Swati Khandelwal Aug 11, 2026 AI Security / Cyber Attack A malicious tool server connected to an AI coding assistant can quietly walk off with SSH keys, environment secrets, source code, and customer data without ever sending one obviously harmful instruction.
By @TheHackersNews · thehackernews.com
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