# CVE-2026-19964: Jij-Inc Jij-MCP-Server jm_check python_repr.py PythonREPL.run code injection

> Remote attackers can execute arbitrary code via the PythonREPL.run function in the Jij-MCP-Server library due to improper input validation.

- **Severity:** Medium 5.1 (`CVSS: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`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 16 Aug 2026
- **Updated:** 18 Aug 2026
- **Also known as:** GHSA-g33m-cxj9-5gvx

## What is CVE-2026-19964?

CVE-2026-19964 is a medium-severity code injection vulnerability in Jij-Inc Jij-MCP-Server, published on 16 Aug 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

A vulnerability was found in Jij-Inc Jij-MCP-Server 0.1.0. This affects the function PythonREPL.run of the file jij_mcp/python_repr.py of the component jm_check. The manipulation of the argument code results in code injection. It is possible to launch the attack remotely. The exploit has been made public and could be used. The project was informed of the problem early through an issue report but has not responded yet.

Weakness: CWE-94 (Improper Control of Generation of Code), CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component)

## Which versions are affected by CVE-2026-19964?


## How do I fix CVE-2026-19964?

No fix has been published for CVE-2026-19964 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-19964 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-19964 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-19964 and fix it if it is affected.

What it is: CVE-2026-19964 is a medium-severity code injection vulnerability in Jij-Inc Jij-MCP-Server, published on 16 Aug 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-19964 exists.

Affected product: Jij-Inc Jij-MCP-Server. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-19964/ (Markdown: https://insights.sbomify.com/CVE-2026-19964/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-19964
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-19964
- OSV: https://osv.dev/vulnerability/CVE-2026-19964

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-19964/
Summaries are generated and may contain mistakes; the official description above is the record.