utcp-cli Command Injection Vulnerability via Unsanitized Argument Substitution (CVE-2026-45369)

The utcp-cli package before version 1.1.2 contains a command injection vulnerability within the _substitute_utcp_args method of cli_communication_protocol.py. This flaw stems from the direct insertion of user-controlled tool_args values into shell command strings without proper sanitization or escaping. Subsequently, these crafted commands are executed using /bin/bash -c on Unix-like systems or powershell.exe -Command on Windows, enabling a malicious actor to inject arbitrary shell commands. This vulnerability poses a significant risk, as it allows for complete Remote Code Execution (RCE) on the affected host. The issue has been addressed in utcp-cli version 1.1.2 by implementing shell-quoting of all substituted values using shlex.quote on Unix and PowerShell single-quoted literals on Windows systems, which mitigates the risk of metacharacter injection. The vulnerability was reported by @ZeroXJacks.

Attack Chain

1. An attacker crafts a malicious payload containing shell metacharacters.
2. The attacker supplies this payload as a value within the tool_args dictionary.
3. The vulnerable _substitute_utcp_args method substitutes the attacker-controlled value into a command string.
4. Due to the lack of sanitization, the command string now contains the injected shell metacharacters.
5. The command string is embedded within a shell script.
6. The shell script is executed using /bin/bash -c or powershell.exe -Command.
7. The injected shell metacharacters are interpreted, executing arbitrary commands.
8. The attacker achieves Remote Code Execution on the host system.

Impact

Successful exploitation of this vulnerability allows an attacker to execute arbitrary commands on the host system with the privileges of the utcp-cli application. This can lead to complete system compromise, including data exfiltration, malware installation, and denial-of-service. Given the severity and ease of exploitation, any system running a vulnerable version of utcp-cli is at critical risk.

Recommendation

• Upgrade utcp-cli to version 1.1.2 or later to remediate CVE-2026-45369.
• Deploy the Sigma rule “Detect utcp-cli Command Injection Attempt via Argument Substitution” to your SIEM and tune for your environment.
• If upgrading is not immediately feasible, restrict or audit user-supplied input to tool_args to mitigate the risk of command injection.