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Vulnerabilities

Vulnerability · CVE-2026-39861

Claude Code is an agentic coding tool.

Published Apr 21, 2026 · catalog updated Jun 17, 2026 · anthropic claude code

Severity
High7.7
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.8%
Remediation
Advisory link
Affected products
cpe anthropic/claude code

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.

Technical analysis

Mechanism and impact are interpreted from ingested advisories — not independent exploit research.

  • CWE classification

    Path Traversal ·

  • Prerequisites and impact

    Follow the original vendor advisory for access prerequisites and impact. This catalog does not invent exploit conditions.

How to fix CVE-2026-39861

What to do

Three reads of the same public record: the decision, the versions on file, and the signals. Confirm the vendor advisory before you patch. This page does not publish exploit steps.

Executive

This is a public record, not a confirmed incident. CVE-2026-39861 is a high issue in anthropic claude code (CVSS 7.7). CISA does not currently list it as known exploited. Next step: Compare installed versions with the linked vendor advisory before changing production.

System administrator

Check whether anthropic claude code is installed. Ranges on record: anthropic/claude code. Compare installed versions with the linked vendor advisory before changing production.

Security analyst

CVSS 7.7. EPSS 0.8%. CISA does not currently list it as known exploited. Weaknesses: CWE-22, CWE-61. Sources: cve_org, epss, nvd. Exploit links, when listed below, point at the original publisher.

Related intelligence

  • Exploitation evidence

    Not listed as known exploited in CISA KEV. Not in CISA KEV or VulnCheck KEV.

  • Safe detection guidance

    Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Apr 21, 2026 · NIST NVD

    Detected

    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 confirmati

  2. Jun 17, 2026 · NIST NVD

    Updated

    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 confirmati

Affected versions

Enter an installed version to get a verified affected / not-affected result against the ranges below.

  • cpe anthropic/claude codeversion unspecified

Sources

  • CVE.orgVulnerability recordCVE-2026-39861

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-39861

    30-day exploitation probability 0.8%

    first.org
  • NIST NVDVulnerability recordCVE-2026-39861

    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 proce

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.