CVE-2026-85660Network attack vector

Arbitrary command execution via shell substitution bypass

Published Sep 4, 2026 · Updated Sep 4, 2026

OS command injection in CLI MCP Server 0.2.5 and earlier allows remote attackers to execute non-allowlisted commands through MCP. The _validate_command_with_operators function splits only on its enumerated operators, validates those command parts, and passes the unchanged input to subprocess.run with shell=True, leaving $() and backticks for the shell to evaluate. Exploitation requires access to the run_command tool and the non-default ALLOW_SHELL_OPERATORS setting; successful commands run with the server process's permissions.

CVSS severity9.2
Critical
EPSS probability0.47%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

OS command injection in CLI MCP Server 0.2.5 and earlier allows remote attackers to execute non-allowlisted commands through MCP. The _validate_command_with_operators function splits only on its enumerated operators, validates those command parts, and passes the unchanged input to subprocess.run with shell=True, leaving $() and backticks for the shell to evaluate. Exploitation requires access to the run_command tool and the non-default ALLOW_SHELL_OPERATORS setting; successful commands run with the server process's permissions.

The record

CVE
CVE-2026-85660
Published
Sep 4, 2026
Updated
Sep 4, 2026
Vendor
MladenSU
Product
CLI MCP Server
Classifications
CWE-78, T1059.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 4, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 4, 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=0 <=0.2.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

MladenSU · CLI MCP Serverversion=0 <=0.2.5

Published CVSS scores

9.2VulnCheckCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
8.1VulnCheckCVSS:3.1/AV:N/AC:H/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 exploitUnconfirmed

Weakness, pattern, technique

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

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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