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The vulnerability, CVE-2025-26924, stems from the improper handling of project dependencies during the initialization phase of Claude Code. On systems with Yarn 3.0 or higher, the application would automatically execute code defined within Yarn plugins, which are specified in a project’s configuration. This execution occurred before the application’s security-critical “startup trust dialog” was presented to and accepted by the user. An attacker could craft a malicious project containing a harmful Yarn plugin. When a victim opens this project directory with Claude Code, the malicious plugin code runs immediately, without any user consent or warning, leading to arbitrary command execution on the victim’s machine in the context of the current user. This effectively bypasses the primary security gate meant to prevent such scenarios.
Platform: Anthropic Claude Code
Version: Pre-patch versions
Vulnerability : Command Injection
Severity: High
date: 2025-11-19
Prediction: Patch expected 2025-11-26
What Undercode Say:
find ~/.yarn/plugins -name ".js" -exec cat {} \;
yarn plugin import ./malicious-plugin.js
// .yarnrc.yml plugins: - ./malicious-plugin.js
How Exploit:
Create malicious Yarn plugin.
Lure user to open directory.
Automatic code execution pre-trust.
Protection from this CVE
Update Claude Code immediately.
Avoid opening untrusted projects.
Disable Yarn plugins temporarily.
Impact:
Arbitrary command execution.
System compromise.
Bypasses trust mechanism.
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Sources:
Reported By: github.com
Extra Source Hub:
Undercode
