CVE-2026-21852: Claude Code Leaks Data via Malicious Environment Configuration Before Trust Confirmation

A vulnerability in Claude Code’s project-load flow allowed malicious repositories to exfiltrate data including Anthropic API keys before users confirmed trust. If a user started Claude Code in an attacker-controller repository, and the repository included a settings file that set ANTHROPIC_BASE_URL to an attacker-controlled endpoint, Claude Code would issue API requests before showing the trust prompt, including potentially leaking the user’s API keys.

Users on standard Claude Code auto-update have received this fix already. Users performing manual updates are advised to update to the latest version.