Claude Code: Sandbox Escape via Symlink Following Allows Arbitrary File Write Outside Workspace
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- Passive
- Attack complexity
- Low
- Attack requirements
- Present
- Impact type
- —
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub.
Summary
Claude Code is an agentic coding tool. Prior to version 2.1.64, 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 version 2.1.64 or later.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| anthropics | claude-code | before 2.1.64 | 2.1.64 | Patch available | CNA |
| — | @anthropic-ai/claude-code (npm) | before 2.1.64 | 2.1.64 | Patch available | GHSA-vp62-r36r-9xqp |
- claude-code Vendoranthropics Affected before 2.1.64 Fixed in 2.1.64 Patch available CNA
- @anthropic-ai/claude-code (npm) Vendor— Affected before 2.1.64 Fixed in 2.1.64 Patch available GHSA-vp62-r36r-9xqp
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:anthropic:claude_code:*:*:*:*:*:node.js:*:* | before 2.1.64 | Vulnerable | anthropics |
- cpe:2.3:a:anthropic:claude_code:*:*:*:*:*:node.js:*:* Versions before 2.1.64 Vulnerable ·anthropics
Remediation
- Fix · CNA claude-code (anthropics) Fixed in 2.1.64
- Fix · GHSA-vp62-r36r-9xqp @anthropic-ai/claude-code (npm) Fixed in 2.1.64 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-39861
- 2026-10-03 Alias added: GHSA-vp62-r36r-9xqp
References
More anthropics Claude Code vulnerabilities
- TI-2025-40558 Claude Code Command Validation Bypass Allows Arbitrary Code Execution CVSS 4.0HIGH 8.7
- TI-2025-36683 Claude Code vulnerable to arbitrary code execution caused by maliciously configured git email CVSS 4.0HIGH 8.7
- TI-2025-37066 Claude Code's startup trust dialog could lead to Command Execution attack CVSS 4.0HIGH 8.7
- TI-2026-17554 Claude Code Leaks Data via Malicious Environment Configuration Before Trust Confirmation CVSS 4.0MEDIUM 5.3
- TI-2025-40093 @anthropic-ai/claude-code has Sed Command Validation Bypass that Allows Arbitrary File Writes CVSS 4.0HIGH 8.7
- TI-2025-36422 Claude Code rg command had Command Injection that allowed bypass of user approval prompt for command execution CVSS 4.0HIGH 8.7
Sources
- CVE-2026-39861 · CVE Program
- CVE-2026-39861 · NVD
- FIRST EPSS
- GHSA-vp62-r36r-9xqp · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences