AI agent vulnerability · Claude Code

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

mediumCVSS 4.0 5.3GHSA-jh7p-qr78-84p7

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 ANTHROPICBASEURL to an attacker-controlled endpoint, Claude Code would issue API requests before showing the trust prompt, including…

Published Jan 21, 2026

Affected packages

@anthropic-ai/claude-code

Ecosystem: npm
Affected: < 2.0.65
Fixed in: 2.0.65
Check: npm ls @anthropic-ai/claude-code

Advisory details

From the GitHub Advisory Database (CC BY 4.0).

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.

References

How this page is made: the data panel comes from the GitHub Advisory Database, CISA’s KEV catalog, the NVD and FIRST EPSS, and updates twice a day. No analysis has been written for this entry yet. Methodology

Coverage on the Beam blog

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