# [CRIT] [GHSA / CRITICAL] CVE-2026-45369: utcp-cli Vulnerable to Command Injection via Unsanitized Argument Substitution in CLI Communication Protocol

**Source:** GitHub Security Advisories
**Published:** 2026-05-14
**Article:** https://github.com/advisories/GHSA-33p6-5jxp-p3x4

## Threat Profile

utcp-cli Vulnerable to Command Injection via Unsanitized Argument Substitution in CLI Communication Protocol

## Summary

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/communi…

## Indicators of Compromise (high-fidelity only)

- **CVE:** `CVE-2026-45369`

## MITRE ATT&CK Techniques

- **T1190** — Exploit Public-Facing Application
- **T1059.001** — PowerShell
- **T1027** — Obfuscated Files or Information
- **T1204.002** — User Execution: Malicious File
- **T1059.004** — Command and Scripting Interpreter: Unix Shell
- **T1068** — Exploitation for Privilege Escalation
- **T1059.006** — Command and Scripting Interpreter: Python

## Kill chain phases observed

_(none detected from narrative keywords)_

## Recommended hunts

### utcp-cli command injection via UTCP_ARG substitution in python→bash -c CMD_N_OUTPUT script

`UC_288_3` · phase: **exploit** · confidence: **High** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats summariesonly=t count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where (Processes.parent_process_name IN ("python","python3","python3.9","python3.10","python3.11","python3.12","python.exe","pythonw.exe")) AND (Processes.process_name IN ("bash","sh","dash","powershell.exe","pwsh.exe")) AND Processes.process="*CMD_*_OUTPUT=$(*" by Processes.dest Processes.user Processes.parent_process_name Processes.parent_process Processes.process_name Processes.process Processes.process_path
| `drop_dm_object_name(Processes)`
| rex field=process "CMD_\d+_OUTPUT=\$\((?<substituted>[^)]+)\)"
| eval injected=if(match(substituted,"(?i)(;\s*(curl|wget|nc|bash|sh|python|perl|powershell|base64|chmod|chown)|`[^`]+`|\$\(\s*(cat|curl|wget|whoami|id|uname|hostname|base64|nc)|\|\s*(sh|bash|nc|base64|tee)|>\s*/(tmp|var|dev|etc)|/etc/(passwd|shadow|hosts)|&&\s*(curl|wget|nc|bash))"),1,0)
| where injected=1
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| table firstTime lastTime dest user parent_process_name parent_process process_name process substituted
```

**Defender KQL:**
```kql
DeviceProcessEvents
| where Timestamp > ago(7d)
| where InitiatingProcessFileName matches regex @"(?i)^python(3(\.\d+)?)?(\.exe|w\.exe)?$"
| where FileName in~ ("bash","sh","dash","powershell.exe","pwsh.exe")
| where ProcessCommandLine matches regex @"CMD_\d+_OUTPUT=\$\("      // utcp-cli's signature script template
| extend Substituted = extract(@"CMD_\d+_OUTPUT=\$\(([^)]+)\)", 1, ProcessCommandLine)
| where ProcessCommandLine matches regex @"(?i)(;\s*(curl|wget|nc|bash|sh|python|perl|powershell|base64|chmod|chown)|`[^`]+`|\$\(\s*(cat|curl|wget|whoami|id|uname|hostname|base64|nc)|\|\s*(sh|bash|nc|base64|tee)|>\s*/(tmp|var|dev|etc)|/etc/(passwd|shadow|hosts)|&&\s*(curl|wget|nc|bash))"
| project Timestamp, DeviceName, AccountName, InitiatingProcessFileName, InitiatingProcessCommandLine, FileName, FolderPath, ProcessCommandLine, Substituted, SHA256
| order by Timestamp desc
```

### Vulnerable utcp-cli package (<= 1.1.1) inventory hunt for CVE-2026-45369

`UC_288_4` · phase: **recon** · confidence: **High** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats summariesonly=t count min(_time) as firstTime max(_time) as lastTime values(Processes.process) as sample_cmd from datamodel=Endpoint.Processes where Processes.process_name IN ("python","python3","python3.9","python3.10","python3.11","python3.12","python.exe","pip","pip3") AND (Processes.process="*utcp_cli*" OR Processes.process="*utcp-cli*" OR Processes.process="*-m utcp*") by Processes.dest Processes.user Processes.process_name
| `drop_dm_object_name(Processes)`
| rex field=sample_cmd "utcp[-_]cli[=<>]+(?<version>\d+\.\d+\.\d+)"
| eval vulnerable=case(isnotnull(version) AND match(version,"^(0\.|1\.0\.|1\.1\.[01])$"),"yes",isnull(version),"unknown_check_pip_freeze",1=1,"no")
| where vulnerable!="no"
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| table firstTime lastTime dest user process_name version vulnerable sample_cmd
```

**Defender KQL:**
```kql
// Approach A — TVM software inventory (fast, no host scan)
DeviceTvmSoftwareInventory
| where SoftwareVendor in~ ("universal-tool-calling-protocol","utcp","pypi")
| where SoftwareName has "utcp" and SoftwareName has "cli"
| extend V = split(SoftwareVersion, ".")
| extend Major = toint(V[0]), Minor = toint(V[1]), Patch = toint(V[2])
| where Major < 1 or (Major == 1 and Minor == 0) or (Major == 1 and Minor == 1 and Patch <= 1)
| project DeviceName, OSPlatform, SoftwareName, SoftwareVersion
| union (
    // Approach B — fallback: pip install / runtime invocation evidence
    DeviceProcessEvents
    | where Timestamp > ago(30d)
    | where InitiatingProcessFileName matches regex @"(?i)^(pip3?|python(3(\.\d+)?)?)(\.exe)?$"
        or FileName matches regex @"(?i)^(pip3?|python(3(\.\d+)?)?)(\.exe)?$"
    | where ProcessCommandLine has_any ("utcp_cli","utcp-cli")
    | summarize Hosts = make_set(DeviceName), LastSeen = max(Timestamp), SampleCmd = any(ProcessCommandLine) by FileName
    | mv-expand DeviceName = Hosts to typeof(string)
    | project DeviceName, OSPlatform="", SoftwareName="utcp-cli (cmdline-evidence)", SoftwareVersion=tostring(SampleCmd)
)
| order by DeviceName asc
```

### PowerShell encoded / obfuscated command

`UC_PS_OBFUSCATED` · phase: **exploit** · confidence: **High**

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime
    from datamodel=Endpoint.Processes
    where Processes.process_name IN ("powershell.exe","pwsh.exe")
      AND (Processes.process="*-enc *" OR Processes.process="*EncodedCommand*"
        OR Processes.process="*FromBase64String*" OR Processes.process="*-nop*"
        OR Processes.process="*-w hidden*" OR Processes.process="*Invoke-Expression*"
        OR Processes.process="*IEX(*" OR Processes.process="*DownloadString*"
        OR Processes.process="*Net.WebClient*")
    by Processes.dest, Processes.user, Processes.process_name, Processes.process, Processes.parent_process_name
| `drop_dm_object_name(Processes)`
```

**Defender KQL:**
```kql
DeviceProcessEvents
| where Timestamp > ago(7d)
| where AccountName !endswith "$"
| where FileName in~ ("powershell.exe","pwsh.exe")
| where ProcessCommandLine matches regex @"(?i)(-enc|encodedcommand|frombase64string|-nop|-w\s+hidden|invoke-expression|iex\s*\(|downloadstring|net\.webclient)"
| project Timestamp, DeviceName, AccountName, ProcessCommandLine,
          InitiatingProcessFileName, InitiatingProcessCommandLine
```

### Article-specific behavioural hunt — [GHSA / CRITICAL] CVE-2026-45369: utcp-cli Vulnerable to Command Injection via U

`UC_288_2` · phase: **exploit** · confidence: **High**

**Splunk SPL (CIM):**
```spl
``` Article-specific bespoke detection — [GHSA / CRITICAL] CVE-2026-45369: utcp-cli Vulnerable to Command Injection via U ```
| tstats `summariesonly` count earliest(_time) AS firstTime latest(_time) AS lastTime
    from datamodel=Endpoint.Processes
    where (Processes.process_name IN ("cli_communication_protocol.py","script.py"))
    by Processes.dest, Processes.user, Processes.process_name,
       Processes.process, Processes.parent_process_name, Processes.process_path
| `drop_dm_object_name(Processes)`
| `security_content_ctime(firstTime)`
| append [
| tstats `summariesonly` count
    from datamodel=Endpoint.Filesystem
    where Filesystem.action IN ("created","modified")
      AND (Filesystem.file_path="*/etc/passwd*" OR Filesystem.file_name IN ("cli_communication_protocol.py","script.py"))
    by Filesystem.dest, Filesystem.user, Filesystem.process_name,
       Filesystem.file_path, Filesystem.file_name
| `drop_dm_object_name(Filesystem)`
]
```

**Defender KQL:**
```kql
// Article-specific bespoke detection — [GHSA / CRITICAL] CVE-2026-45369: utcp-cli Vulnerable to Command Injection via U
// Hunts the actual binaries / paths / commandline fragments named
// in the article instead of a generic technique-class template.
DeviceProcessEvents
| where Timestamp > ago(30d)
| where (FileName in~ ("cli_communication_protocol.py", "script.py"))
| project Timestamp, DeviceName, AccountName, FileName,
          FolderPath, ProcessCommandLine,
          InitiatingProcessFileName, InitiatingProcessCommandLine
| order by Timestamp desc

// File-creation events for the named binaries / paths
DeviceFileEvents
| where Timestamp > ago(30d)
| where ActionType in ("FileCreated","FileModified")
| where (FolderPath has_any ("/etc/passwd") or FileName in~ ("cli_communication_protocol.py", "script.py"))
| project Timestamp, DeviceName, AccountName, FolderPath,
          FileName, ActionType, InitiatingProcessFileName,
          InitiatingProcessCommandLine
| order by Timestamp desc
```

### IOC-driven hunts (use shared templates)

These are standard IOC-substitution hunts — the canonical SPL and KQL live once in [`_TEMPLATES.md`](../_TEMPLATES.md), so we don't repeat the same boilerplate on every CVE / hash / network-IOC briefing.

- **Asset exposure — vulnerability matches article CVE(s)** ([template](../_TEMPLATES.md#asset-exposure)) — phase: **recon**, confidence: **High**
  - CVE(s): `CVE-2026-45369`


## Why this matters

Severity classified as **CRIT** based on: CVE present, 5 use case(s) fired, 7 technique(s) inferred. Read the full article for actor attribution, tooling details, and any defanged IOCs in the body that aren't visible in the RSS summary.