Vulnerability in Anthropic Claude Code

CVE-2026-21852

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.

Published · last modified .

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.279 (98.0th percentile), scored .

Moderate probability of exploitation in the next 30 days — watch for active exploitation reports. 98th percentile — 98.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-21852: rose from 0.243 to 0.279.

EPSS over last 30 days · oldest: 0.243 · newest: 0.279 · change: +0.036

Affected products

Weakness classification (CWE)

Public proof-of-concept exploits

References

Frequently asked questions

What is CVE-2026-21852?
CVE-2026-21852 is a high-severity vulnerability in Anthropic Claude Code, classified under Insufficiently Protected Credentials. CVSS score: 7.5/10. Published 2026-01-21.
How severe is CVE-2026-21852?
High severity. CVSS v3 base score is 7.5 out of 10.
Is CVE-2026-21852 known to be exploited?
5 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.