CVE-2026-39861: Claude Code is an agentic coding tool

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CRITICAL 10.0REMOTEUPGRADE

CVE-2026-39861 is a critical-severity flaw (CVSS 10.0) affecting claude code. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 th

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	10.0 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.7% (top 47%)
CISA exploited list	No
Weakness	CWE-22, CWE-61
Published	2026-04-21
Last modified	2026-10-26

Publisher (CNA): GitHub, Inc. · Vendor: anthropic

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-21 01:16 UTCPublished CVE record published
2026-10-26 22:10 UTCUpdated Record last modified

anthropic claude code UPGRADE

Affected: < 2.1.64

Fixed in: 2.1.64

Safe to downgrade to: no unaffected older release

1. Check installed version

npm ls claude-code

2. UPGRADE to 2.1.64

npm install claude-code@">=2.1.64"

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-39861?

claude code: upgrade to 2.1.64. Exact commands for each OS are on this page.

Is CVE-2026-39861 being exploited?

CVE-2026-39861 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-39861 affect?

CVE-2026-39861 affects claude code. Severity is critical (CVSS 10.0). 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 with

How urgent is CVE-2026-39861?

Priority 53/100. Critical severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-35603 HIGH 7.3 UPGRADE Claude Code is an agentic coding tool
CVE-2026-54316 CRITICAL 9.1 UPGRADE Claude Code is an agentic coding tool
CVE-2026-55607 HIGH 8.8 UPGRADE Claude Code is an agentic coding tool
CVE-2026-46406 MEDIUM 6.1 UPGRADE Claude Code is an agentic coding tool

References

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