CVE-2026-25725: Claude Code Has Sandbox Escape via Persistent Configuration Injection in settings.json
Claude Code is an agentic coding tool. Prior to version 2.1.2, Claude Code's bubblewrap sandboxing mechanism failed to properly protect the .claude/settings.json configuration file when it did not exist at startup. While the parent directory was mounted as writable and .claude/settings.local.json was explicitly protected with read-only constraints, settings.json was not protected if it was missing. This allowed malicious code running inside the sandbox to create this file and inject persistent hooks (such as SessionStart commands) that would execute with host privileges when Claude Code was restarted. This issue has been patched in version 2.1.2.
Other sources
Claude Code's bubblewrap sandboxing mechanism failed to properly protect the .claude/settings.json configuration file when it did not exist at startup. While the parent directory was mounted as writable and .claude/settings.local.json was explicitly protected with read-only constraints, settings.json was not protected if it was missing. This allowed malicious code running inside the sandbox to create this file and inject persistent hooks (such as SessionStart commands) that would execute with host privileges when Claude Code was restarted.
Users on standard Claude Code auto-update received this fix automatically. Users performing manual updates are advised to update to the latest version.
Claude Code thanks hackerone.com/edbr for reporting this issue!
— GitHub
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-25725?
CVE-2026-25725 has a medium severity rating due to its potential for sandbox escape.
How do I fix CVE-2026-25725?
To fix CVE-2026-25725, upgrade Claude Code to version 2.1.2 or higher.
What is the nature of the vulnerability in CVE-2026-25725?
CVE-2026-25725 is a sandbox escape vulnerability due to improper protection of the settings.json file.
Which versions of Claude Code are affected by CVE-2026-25725?
CVE-2026-25725 affects all versions of Claude Code prior to 2.1.2.
What type of software is impacted by CVE-2026-25725?
CVE-2026-25725 impacts Claude Code, an agentic coding tool.