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CVE-2026-39861 — Vulnerability in @anthropic-ai/claude-code — CVE...

HIGH

Claude Code: Sandbox Escape via Symlink Following Allows Arbitrary File Write Outside Workspace

Published April 21, 2026Updated May 5, 2026Source: osv

Summary

Claude Code's sandbox did not prevent sandboxed processes from creating symlinks pointing to locations outside the workspace. When Claude Code subsequently wrote to a path within such a symlink, its unsandboxed process followed the symlink and wrote to the target location outside the workspace without prompting the user for confirmation. This allowed a sandbox escape where neither the sandboxed command nor the unsandboxed app could independently write outside the workspace, but their combination could write to arbitrary locations, potentially leading to code execution outside the sandbox. Reliably exploiting this required the ability to add untrusted content into a Claude Code context window to trigger sandboxed code execution via prompt injection. Users on standard Claude Code auto-update have received this fix automatically. Users performing manual updates are advised to update to the latest version. Claude Code thanks hackerone.com/philts for reporting this issue.

Advisory Timeline

  • First published April 21, 2026 (174 days ago).
  • Last revised May 5, 2026 — 14 days after initial publication.

Remediation

Upgrade to the fixed version using your package manager.

npm
Update @anthropic-ai/claude-code to 2.1.64 or later
npm install @anthropic-ai/claude-code@2.1.64

After upgrading, run your dependency scanner again to confirm the vulnerability is resolved.

Affected Packages (1)

Affects 1 ecosystem: npm (1).

PackageEcosystemAffectedFixed In
@anthropic-ai/claude-code
npm
All versions2.1.64

Vulnerability Classification

Common Weakness Enumeration (CWE) identifiers for this vulnerability type.

CVSS Score Breakdown

What the CVSS (Common Vulnerability Scoring System) 10.0 score means for each attack dimension.

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

References

Frequently Asked Questions

What is CVE-2026-39861?
Claude Code: Sandbox Escape via Symlink Following Allows Arbitrary File Write Outside Workspace This vulnerability has been assigned a severity rating of HIGH (CVSS score: 10.0/10).
How do I check if my project is affected by CVE-2026-39861?
CVE-2026-39861 affects @anthropic-ai/claude-code. Use GeekWala's free vulnerability scanner to check your dependencies against CVE-2026-39861 and 200,000+ other known vulnerabilities.

Severity & Exploitability

CVSS Score
10.0

Exploitation is straightforward and causes maximum impact. Patch immediately.

Also Known As

GHSA-vp62-r36r-9xqp

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