CVE-2026-58390 — OPNsense is a FreeBSD based firewall and routing platform.¶
Key facts
CVE-2026-58390 is a High (8.0) vulnerability: OPNsense is a FreeBSD based firewall and routing platform.. This entry ships a detection-only PoC and a Docker test lab.
| CVE | CVE-2026-58390 |
| Severity | High (8.0) |
| Detection / prevention | — |
| PoC | poc.py |
| Source | 2026/CVE-2026-58390/ |
Details¶
English | 한국어
Description¶
OPNsense is a FreeBSD based firewall and routing platform. Prior to version 26.1.11, the OpenVPN connection-status dashboard widget in src/opnsense/www/js/widgets/OpenVPNClients.js and the connection-status view place a client common_name into data-common-name attributes without quote-safe encoding. Exploitation requires an OpenVPN server configured with username-as-common-name and RADIUS or LDAP authentication, plus the ability to provision or self-register a valid backend username containing a double quote; deployments where the same administrator controls both the identity backend and firewall do not cross a separate trust boundary. An authenticated client using that username can close the attribute and add an event handler, while the local user database is not affected because its username validator rejects quotes. Script executes in an administrator's session when the administrator opens the dashboard or connection-status page and the injected event is triggered; the demonstrated payload used pointer movement over the client row rather than unconditional page-load execution. The advisory demonstrates that the script can read config.xml, invoke privileged APIs, reset the root password, and obtain root command execution. This issue is fixed in version 26.1.11.
Vulnerability Details¶
| Property | Value |
|---|---|
| CVE ID | CVE-2026-58390 |
| Type | XSS |
| CVSS Score | 8.0 |
Proof of Concept¶
Download¶
# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2026/CVE-2026-58390/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-2026-58390
# 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/opnsense/core/commit/11180daf579879d84d91a7fbea7a59320bc80868
- https://github.com/opnsense/core/commit/e7b2ac8093f804bef8eb88dfa9a0d99fad00c12b
- https://github.com/opnsense/core/security/advisories/GHSA-26cj-h9rj-g5pf
Generated by PoC Generator on 2026-10-16T03:04:23.3597136
Frequently asked questions¶
What is CVE-2026-58390?¶
CVE-2026-58390 is a High (8.0) vulnerability: OPNsense is a FreeBSD based firewall and routing platform.. This entry ships a detection-only PoC and a Docker test lab.
How do I detect CVE-2026-58390?¶
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-2026-58390?¶
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.