CVE-2026-86121 — Cua computer-server versions before 0.3.42 skip authentication when the CONTAINER_NAME…¶
Key facts
CVE-2026-86121 is a Critical (9.8) vulnerability: Cua computer-server versions before 0.3.42 skip authentication when the CONTAINER_NAME…. This entry ships a detection-only PoC and a Docker test lab.
| CVE | CVE-2026-86121 |
| Severity | Critical (9.8) |
| Detection / prevention | — |
| PoC | poc.py |
| Source | 2026/CVE-2026-86121/ |
Details¶
English | 한국어
Description¶
Cua computer-server versions before 0.3.42 skip authentication when the CONTAINER_NAME environment variable is unset and bind to all interfaces by default, allowing unauthenticated attackers to execute arbitrary commands. Attackers can reach TCP port 8000 to run shell commands via the run_command endpoint, read and write arbitrary files through file operation endpoints, and access interactive PTY shells without authentication.
Vulnerability Details¶
| Property | Value |
|---|---|
| CVE ID | CVE-2026-86121 |
| CVSS Score | 9.8 |
Proof of Concept¶
Download¶
# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2026/CVE-2026-86121/poc.py
Usage¶
# Run PoC against target
python3 poc.py --target <TARGET_URL>
# With authentication
python3 poc.py --target <TARGET_URL> --username <USER> --password <PASS>
⚠️ Warning: This PoC is for authorized security testing only. It uses detection-only techniques and does not exploit or damage target systems.
Test Lab¶
This repository includes a Docker-based test environment with both vulnerable and patched applications.
Quick Start¶
# Clone and navigate to CVE directory
cd CVE-2026-86121
# Start both applications
docker-compose up -d
# Run tests
./run-tests.sh # Linux/Mac
./run-tests.ps1 # Windows PowerShell
Application Endpoints¶
| Application | URL | Status |
|---|---|---|
| Vulnerable App | http://localhost:8080 | Shows vulnerability |
| Patched App | http://localhost:8081 | Demonstrates fix |
Directory Structure¶
├── README.md # English documentation
├── README_KO.md # Korean documentation
├── poc.py # PoC detection script
├── docker-compose.yml # Container orchestration
├── run-tests.sh # Linux/Mac test runner
├── run-tests.ps1 # Windows test runner
├── vulnerable-app/ # Vulnerable version
│ ├── app.py
│ ├── Dockerfile
│ └── requirements.txt
└── patched-app/ # Fixed version
├── app.py
├── Dockerfile
└── requirements.txt
References¶
- https://github.com/trycua/cua
- https://github.com/trycua/cua/blob/10a2e71792db/libs/python/computer-server/computer_server/cli.py
- https://github.com/trycua/cua/blob/10a2e71792db/libs/python/computer-server/computer_server/main.py
- https://github.com/trycua/cua/commit/59cf25c0ec54
- https://github.com/trycua/cua/issues/1892
- https://www.vulncheck.com/advisories/cua-computer-server-before-0.3.42-unauthenticated-rce-via-desktop-control
Generated by PoC Generator on 2026-09-05T21:02:12.383388751
Frequently asked questions¶
What is CVE-2026-86121?¶
CVE-2026-86121 is a Critical (9.8) vulnerability: Cua computer-server versions before 0.3.42 skip authentication when the CONTAINER_NAME…. This entry ships a detection-only PoC and a Docker test lab.
How do I detect CVE-2026-86121?¶
Run the detection-only PoC included with this entry against your Docker test lab to confirm whether a target is affected; pair it with your own IDS logging.
How do I block or mitigate CVE-2026-86121?¶
Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.
For authorized security testing and research only. See the full source and NVD record.