MCP FOR AGENT-TO-AGENT COMMS MAY BE THE RISKIEST PROTOCOL YOU'VE NEVER HEARD OF

Summary from the TLDR InfoSec newsletter

Google and four other organizations acknowledged flaws over the past five months where a prompt injection landing on one AI agent over MCP was forwarded to other internal agents, which executed it on trust. Researcher Syed Anas Mohiuddin named the technique "protocol pivoting," though X41 D-Sec's Markus Vervier told Ars Technica it is plain indirect prompt injection. The bugs typically ended in SSRF, ranging from severity 2.7 at Rapid7 (CVE-2026-97228) to 8 in Google's mcp-toolbox, which followed redirects without validating target IPs.