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CVE-2026-39861

Anthropic Claude Code path traversal

10.0 CRITICALEPSS 0.80%
  1. Published20 Apr 2026

Description

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeChanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Affected products

Anthropic Claude Code< 2.1.64

Remediation

Fixed in
Anthropic Claude Code≥ 2.1.64

References

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Frequently asked

Is CVE-2026-39861 being actively exploited?

CVE-2026-39861 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.80%.

How severe is CVE-2026-39861?

CVE-2026-39861 has a CVSS 3.1 base score of 10.0, rated critical. EPSS estimates a 0.80% probability of exploitation.

Which products are affected by CVE-2026-39861?

Affected products include Anthropic Claude Code.

How do I fix CVE-2026-39861?

Upgrade affected software to a fixed version, for example Anthropic Claude Code 2.1.64 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-39861 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.