How severe is CVE-2026-21852?

CVE-2026-21852 has a CVSS 4.0 base score of 5.3 (MEDIUM). EPSS estimates a 27.9% probability of exploitation in the next 30 days.

CVE-2026-21852: Claude Code Leaks Data via Malicious Environment

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.

Severity

CVSS 4.0 · CNA5.3 MEDIUM

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

SSVC · CISA-ADP

Exploitationnone

Automatableyes

Technical impactpartial

Affected Products

Vendor	Product	Affected versions
anthropics	claude-code	< 2.0.65

References

1 Links

Other references

https://github.com/anthropics/claude-code/security/advisories/GHSA-jh7p-qr78-84p7

Record Details

Published

2026-01-21

Last updated

2026-01-21

Assigner (CNA)

GitHub_M

Credited to

Related Tool Categories

Tool categories that test for or protect against this vulnerability class.

CWE-522 · Insufficiently Protected Credentials

IAM Tools Application Security Tools

CVE record data © The MITRE Corporation, used under the CVE Terms of Use. Exploited-in-the-wild data from the CISA Known Exploited Vulnerabilities catalog (CC0). Exploit prediction scores by FIRST EPSS (first.org/epss). This site is not endorsed or certified by MITRE, NVD, CISA, or FIRST.