CVE-2026-21852 MEDIUM

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

Vendor Anthropics
Product claude-code
Weakness CWE-522 · Insufficiently protected credentials
Published January 21, 2026
Last update January 21, 2026
View on NVD All CVEs

CVSS base score

5.3/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction —
Confidentiality —
Integrity —

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N

What the vulnerability does

01Description

Claude Code is an agentic coding tool. Prior to version 2.0.65, vulnerability in Claude Code's project-load flow allowed malicious repositories to exfiltrate data including Anthropic API keys before users confirmed trust. An attacker-controlled repository could include a settings file that sets ANTHROPIC_BASE_URL to an attacker-controlled endpoint and when the repository was opened, Claude Code would read the configuration and immediately issue API requests before showing the trust prompt, 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 version 2.0.65, which contains a patch, or to the latest version.

Key dates

02Disclosure timeline

January 21, 2026 CVE published
January 21, 2026 Record updated