🛡️ CVE-2026-39861 — claude-code

🔴 CVSS 10.0 — Critical ✅ No Known Exploit CWE-22 NVD
10.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

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

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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is changed, meaning a successful attack can affect components beyond the vulnerable one. Rated impact: confidentiality high, integrity high, availability high.

Weakness class

CVE-2026-39861 is classified as CWE-22: Path Traversal. A file path built from user input is not confined to the intended directory, letting an attacker reach files elsewhere on the filesystem.

Affected software

CVE-2026-39861 is recorded against 2 packages.

  • @anthropic-ai/claude-code
  • claude-code (fixed in 2.1.64)

Timeline and source

Published on 21 April 2026 and last revised on 5 May 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

github.com (Web)
nvd.nist.gov (Advisory)
github.com (Package)

Details

Severity HIGH
CVSS Score 10.0
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
CWE CWE-22
Public Exploit ✅ No
Source NVD
Published 2026-04-21
Updated 2026-08-12
Modified 2026-05-05
Fix URL N/A

Affected Packages

Software From version Fixed in
@anthropic-ai/claude-code — —
claude-code — 2.1.64

Similar Threats

Exploit Protection

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CVE-2026-39861 carries CVSS 10.0 Critical rating. BotEraser checks your installation against this and other known CVE records, and blocks IPs associated with exploit activity.

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