CVE-2026-19964Public exploitNetwork attack vector

Authenticated code execution via exec in jm_check

Published Aug 16, 2026 · Updated Aug 16, 2026

Code injection in jm_check in JIJ Inc. Jij MCP Server 0.1.0 allows remote authenticated users to execute Python code via the code argument. The jijmodeling_check function in jij_mcp/jm_checker.py passes caller-controlled input to PythonREPL.run, which executes exec(code) in jij_mcp/python_repr.py with no sandbox, restricted builtins, or subprocess isolation. Exploitation requires access to invoke the jm_check MCP tool, but one crafted call can run operating-system commands with the MCP server process's privileges.

CVSS severityUnavailable
Unscored
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Code injection in jm_check in JIJ Inc. Jij MCP Server 0.1.0 allows remote authenticated users to execute Python code via the code argument. The jijmodeling_check function in jij_mcp/jm_checker.py passes caller-controlled input to PythonREPL.run, which executes exec(code) in jij_mcp/python_repr.py with no sandbox, restricted builtins, or subprocess isolation. Exploitation requires access to invoke the jm_check MCP tool, but one crafted call can run operating-system commands with the MCP server process's privileges.

The record

CVE
CVE-2026-19964
Published
Aug 16, 2026
Updated
Aug 16, 2026
Vendor
JIJ Inc.
Product
Jij MCP Server
Classifications
CWE-74, CWE-94, T1059.006
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 16, 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=0.1.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

JIJ Inc. · Jij MCP Serverversion=0.1.0

Published CVSS scores

5.5VulDB CNACVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:L/E:P/RL:X/RC:R
6.5VulDB CNAAV:N/AC:L/Au:S/C:P/I:P/A:P/E:POC/RL:ND/RC:UR
5.1VulDB CNACVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P
5.5VulDB CNACVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:L/E:P/RL:X/RC:R

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
CWE-94Improper Control of Generation of Code ('Code Injection')
T1059.006Python

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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