CVE-2026-39861Network attack vector

Sandbox escape via unsafe symlink following

Published Apr 21, 2026 · Updated Apr 21, 2026

Path traversal in Anthropic Claude Code before 2.1.64 allows remote attackers to write arbitrary files outside the workspace via symlinks. A sandboxed process can create a symlink to an external location, and the unsandboxed application later follows it while writing without a confirmation prompt. Exploitation requires untrusted content to enter a Claude Code context and trigger sandboxed code execution through prompt injection; the resulting write can enable code execution outside the sandbox.

CVSS severity7.7
High
EPSS probability0.71%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Path traversal in Anthropic Claude Code before 2.1.64 allows remote attackers to write arbitrary files outside the workspace via symlinks. A sandboxed process can create a symlink to an external location, and the unsandboxed application later follows it while writing without a confirmation prompt. Exploitation requires untrusted content to enter a Claude Code context and trigger sandboxed code execution through prompt injection; the resulting write can enable code execution outside the sandbox.

The record

CVE
CVE-2026-39861
Published
Apr 21, 2026
Updated
Apr 21, 2026
Vendor
Anthropic
Product
Claude Code
Classifications
CWE-22, CWE-61, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2.1.64

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Anthropic · Claude Codeversion=< 2.1.64

Published CVSS scores

7.7GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
10.0NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
CWE-61UNIX Symbolic Link (Symlink) Following
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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