# CVE-2026-45369: python-utcp: Command Injection via Unsanitized Argument Substitution in CLI Communication Protocol

> Attackers can execute arbitrary shell commands by injecting malicious arguments into the python-utcp library's CLI communication protocol.

- **Severity:** High 8.3 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 14 May 2026
- **Updated:** 16 May 2026
- **Also known as:** GHSA-33p6-5jxp-p3x4, PYSEC-2026-560

## What is CVE-2026-45369?

CVE-2026-45369 is a high-severity command injection vulnerability in universal-tool-calling-protocol python-utcp, published on 14 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

python-utcp is the python implementation of UTCP. Prior to 1.1.3, the _substitute_utcp_args method in cli_communication_protocol.py inserts user-controlled tool_args values directly into shell command strings without any sanitization or escaping. These commands are then executed via /bin/bash -c (Unix) or powershell.exe -Command (Windows), allowing an attacker to inject arbitrary shell commands. This vulnerability is fixed in 1.1.3.

Weakness: CWE-78 (Improper Neutralization of Special Elements used in an OS Command)

## Which versions are affected by CVE-2026-45369?

3 open source packages ship an affected version, including utcp-cli.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `utcp-cli` | PyPI | All versions | 1.1.2 |
| `utcp-cli` | PyPI | All versions | 1.1.2 |
| `utcp-cli` | PyPI | All versions | 1.1.2 |

## How do I fix CVE-2026-45369?

Upgrade utcp-cli to 1.1.2 or later.

## Is CVE-2026-45369 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-45369 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-45369 and fix it if it is affected.

What it is: CVE-2026-45369 is a high-severity command injection vulnerability in universal-tool-calling-protocol python-utcp, published on 14 May 2026. An attacker can exploit it over the internet without logging in, 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-2026-45369 exists.

Affected packages and fixed versions:
- utcp-cli (PyPI): affected all versions; fixed in 1.1.2
- utcp-cli (PyPI): affected all versions; fixed in 1.1.2
- utcp-cli (PyPI): affected all versions; fixed in 1.1.2

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-2026-45369/ (Markdown: https://insights.sbomify.com/CVE-2026-45369/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45369
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45369
- OSV: https://osv.dev/vulnerability/CVE-2026-45369

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-45369/
Summaries are generated and may contain mistakes; the official description above is the record.