CVE-2025-64755Public exploitNetwork attack vector

Arbitrary file writes via misparsed sed syntax

Published Nov 21, 2025 · Updated Nov 21, 2025

Command validation bypass in Anthropic Claude Code before 2.0.31 allows remote attackers to write arbitrary host files through sed. The read-only Bash classifier fails to recognize a sed write command when the w operation and destination lack separating whitespace, although sed executes that syntax as a file write. Exploitation requires untrusted repository, webpage, or MCP content to influence the model into issuing the crafted command; writes run with the Claude Code user's permissions.

CVSS severity8.7
High
EPSS probability0.55%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Command validation bypass in Anthropic Claude Code before 2.0.31 allows remote attackers to write arbitrary host files through sed. The read-only Bash classifier fails to recognize a sed write command when the w operation and destination lack separating whitespace, although sed executes that syntax as a file write. Exploitation requires untrusted repository, webpage, or MCP content to influence the model into issuing the crafted command; writes run with the Claude Code user's permissions.

The record

CVE
CVE-2025-64755
Published
Nov 21, 2025
Updated
Nov 21, 2025
Vendor
Anthropic
Product
Claude Code
Classifications
CWE-78, T1059.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 21, 2025CVE publishedPublication date reported by the CVE source.
  2. Nov 21, 2025Record 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=< 2.0.31

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Anthropic · Claude Codeversion=< 2.0.31

Published CVSS scores

8.7GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/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 exploitPublished

Weakness, pattern, technique

CWE-78Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
T1059.004Unix Shell

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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