CVE-2026-21852: @anthropic ai/claude code Claude Code Leaks Data Vulnerability

MODERATE
Advisory Identifier: GHSA-jh7p-qr78-84p7
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CWE-522
Published
Advisory Summary

CVE-2026-21852 is a MODERATE claude code leaks data vulnerability (CWE-522: Insufficiently Protected Credentials) affecting @anthropic ai/claude code libraries in the npm ecosystem. The issue involves claude code leaks data via malicious environment configuration before trust confirmation. Remediation is available by upgrading affected packages to version 2.0.65.

CVE-2026-21852 at a Glance

CVE Identifier CVE-2026-21852
GHSA Identifier GHSA-jh7p-qr78-84p7
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-522: Insufficiently Protected Credentials
Affected Product @anthropic ai/claude code
Package Ecosystem npm
Published Date
Last Updated

How to Fix CVE-2026-21852

To remediate this vulnerability, upgrade all affected @anthropic ai/claude code dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

@anthropic-ai/claude-code fixed: 2.0.65 
npm install @anthropic-ai/claude-code@2.0.65
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls @anthropic-ai/claude-code

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-21852, inspect your project dependencies using npm:

npm ls @anthropic-ai/claude-code

Analyze the terminal output to locate any version of @anthropic ai/claude code in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.0.65), your application is affected.

Note: The npm ls @anthropic-ai/claude-code command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-522: Insufficiently Protected Credentials, where the product transmits or stores authentication credentials, but it uses an insecure method that is susceptible to unauthorized interception and/or retrieval. In @anthropic ai/claude code, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

A vulnerability in Claude Code's project-load flow allowed malicious repositories to exfiltrate data including Anthropic API keys before users confirmed trust. If a user started Claude Code in an attacker-controller repository, and the repository included a settings file that set ANTHROPIC_BASE_URL to an attacker-controlled endpoint, Claude Code would issue API requests before showing the trust prompt, including 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 the latest version.

CVE-2026-21852 Affected @anthropic ai/claude code Versions

1 component(s)
Fixed Versions:
2.0.65
Product / Package Ecosystem Affected Versions Fixed Version
@anthropic-ai/claude-code
npm/@anthropic-ai/claude-code
npm
< 2.0.65
2.0.65

References

GitHub Advisory / Wiki ADVISORY
https://github.com/anthropics/claude-code/security/advisories/GHSA-jh7p-qr78-84p7
NVD — CVE-2026-21852 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-21852
@anthropic ai/claude code Source Repository REPOSITORY
https://github.com/anthropics/claude-code

Frequently Asked Questions

What is CVE-2026-21852?
CVE-2026-21852 is a security vulnerability in @anthropic ai/claude code involving Claude Code Leaks Data via Malicious Environment Configuration Before Trust Confirmation under CWE-522: Insufficiently Protected Credentials.
Which @anthropic ai/claude code versions are affected?
Affected versions include releases prior to 2.0.65 across affected packages: @anthropic-ai/claude-code.
What version fixes CVE-2026-21852?
Upgrading to 2.0.65 (or the latest patched release for your respective branch) resolves the vulnerability.
Is @anthropic-ai/claude-code affected?
Yes, @anthropic-ai/claude-code is affected in releases prior to 2.0.65. Upgrade your dependency to 2.0.65 or later.
What CWE is associated with CVE-2026-21852?
CVE-2026-21852 is classified under CWE-522: Insufficiently Protected Credentials (The product transmits or stores authentication credentials, but it uses an insecure method that is susceptible to unauthorized interception and/or retrieval.).
How can I check npm dependencies for CVE-2026-21852?
Run the dependency tree command: 'npm ls @anthropic-ai/claude-code'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-jh7p-qr78-84p7",
  "modified" : "2026-01-21T21:40:17Z",
  "published" : "2026-01-21T01:00:31Z",
  "aliases" : [ "CVE-2026-21852" ],
  "summary" : "Claude Code Leaks Data via Malicious Environment Configuration Before Trust Confirmation",
  "details" : "A vulnerability in Claude Code's project-load flow allowed malicious repositories to exfiltrate data including Anthropic API keys before users confirmed trust. If a user started Claude Code in an attacker-controller repository, and the repository included a settings file that set ANTHROPIC_BASE_URL to an attacker-controlled endpoint, Claude Code would issue API requests before showing the trust prompt, including potentially leaking the user's API keys.\n\nUsers on standard Claude Code auto-update have received this fix already. Users performing manual updates are advised to update to the latest version.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@anthropic-ai/claude-code"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.0.65"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/anthropics/claude-code/security/advisories/GHSA-jh7p-qr78-84p7"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-21852"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/anthropics/claude-code"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-522" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-01-21T01:00:31Z",
    "nvd_published_at" : "2026-01-21T21:16:08Z"
  }
}