CVE-2026-12537 is a critical OS command injection vulnerability in Google's Gemini CLI container launcher. It allows an unprivileged attacker to execute arbitrary code on the host of a headless CI platform via a crafted .gemini/.env file. The vulnerability has a CVSS v4 score of 10.0 and is fixed in Gemini CLI 0.39.1 and run-gemini-cli 0.1.22.