CVE-2026-21852 Claude Code Leaks Data via Malicious Environment Configuration Before Trust Confirmation
Malicious repositories can leak Anthropic API keys by triggering API requests before user trust confirmation in Claude Code.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-21852?
CVE-2026-21852 is a medium-severity vulnerability in anthropics claude-code, published on 21 Jan 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
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.
Weakness: CWE-522
Which versions are affected by CVE-2026-21852?
2 open source packages ship an affected version, including @anthropic-ai/claude-code. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
@anthropic-ai/claude-code npm | All versions | 2.0.65 |
@anthropic-ai/claude-code npm | All versions | 2.0.65 |
Products include Anthropic Claude Code.
How do I fix CVE-2026-21852?
Upgrade @anthropic-ai/claude-code to 2.0.65 or later.
Is CVE-2026-21852 being exploited?
There is no known exploitation of CVE-2026-21852 in the wild and no public exploit code.
Public exploit code: 4 proofs of concept on GitHub.
Other vulnerabilities in anthropics claude-code
- CVE-2025-66032 Claude Code Command Validation Bypass Allows Arbitrary Code Execution
- CVE-2025-64755 @anthropic-ai/claude-code has Sed Command Validation Bypass that Allows Arbitrary File Writes
- CVE-2025-59536 Claude Code's startup trust dialog could lead to Command Execution attack
- CVE-2025-58764 Claude Code rg command had Command Injection that allowed bypass of user approval prompt for command execution
- CVE-2025-59041 Claude Code vulnerable to arbitrary code execution caused by maliciously configured git email
Sources
Also known as GHSA-jh7p-qr78-84p7.