Vulnerability · Published Jan 21, 2026 · Assigned by GitHub_M
CVE-2026-21852Claude Code Leaks Data via Malicious Environment Configuration Before Trust Confirmation
Medium 5.3
In plain English
A medium-severity security flaw in claude-code from anthropics. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 27.5% (higher than 98% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| npm | @anthropic-ai/claude-code | 2.0.65 | GHSA-jh7p-qr78-84p7 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| anthropics | claude-code | < 2.0.65 |
Weakness: CWE-522 · 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