Anthropic claude-code up to 2.1.63 Symlink path traversal

Summaryinfo

A vulnerability classified as critical has been found in Anthropic claude-code up to 2.1.63. This affects an unknown function of the component Symlink Handler. This manipulation causes path traversal. The identification of this vulnerability is CVE-2026-39861. It is possible to initiate the attack remotely. There is no exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in Anthropic claude-code up to 2.1.63. Affected by this vulnerability is some unknown processing of the component Symlink Handler. The manipulation with an unknown input leads to a path traversal vulnerability. The CWE definition for the vulnerability is CWE-22. The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-39861 since 04/07/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1006 according to MITRE ATT&CK.

The vulnerability scanner Nessus provides a plugin with the ID 310131 (Anthropic Claude Code < 2.1.64 Sandbox Escape via Symlink Following (CVE-2026-39861)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 2.1.64 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (310131) and EUVD (EUVD-2026-24033). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

• Artificial Intelligence Software

Vendor

• Anthropic

Name

• claude-code

Version

• 2.1.0
• 2.1.1
• 2.1.2
• 2.1.3
• 2.1.4
• 2.1.5
• 2.1.6
• 2.1.7
• 2.1.8
• 2.1.9
• 2.1.10
• 2.1.11
• 2.1.12
• 2.1.13
• 2.1.14
• 2.1.15
• 2.1.16
• 2.1.17
• 2.1.18
• 2.1.19
• 2.1.20
• 2.1.21
• 2.1.22
• 2.1.23
• 2.1.24
• 2.1.25
• 2.1.26
• 2.1.27
• 2.1.28
• 2.1.29
• 2.1.30
• 2.1.31
• 2.1.32
• 2.1.33
• 2.1.34
• 2.1.35
• 2.1.36
• 2.1.37
• 2.1.38
• 2.1.39
• 2.1.40
• 2.1.41
• 2.1.42
• 2.1.43
• 2.1.44
• 2.1.45
• 2.1.46
• 2.1.47
• 2.1.48
• 2.1.49
• 2.1.50
• 2.1.51
• 2.1.52
• 2.1.53
• 2.1.54
• 2.1.55
• 2.1.56
• 2.1.57
• 2.1.58
• 2.1.59
• 2.1.60
• 2.1.61
• 2.1.62
• 2.1.63

CPE 2.3info

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CPE 2.2info

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