CVE-2026-84128 — Privilege escalation in the WebDriver BiDi component.¶

Key facts

CVE-2026-84128 is a High (8.8) vulnerability: Privilege escalation in the WebDriver BiDi component.. This entry ships a detection-only PoC and a Docker test lab.


CVE	CVE-2026-84128
Severity	High (8.8)
Detection / prevention	—
PoC	poc.py
Source	2026/CVE-2026-84128/

Details¶

English | 한국어

Description¶

Privilege escalation in the WebDriver BiDi component. This vulnerability was fixed in Firefox 155 and Thunderbird 155.

Vulnerability Details¶

Property	Value
CVE ID	CVE-2026-84128
CVSS Score	8.8

Proof of Concept¶

Download¶

# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2026/CVE-2026-84128/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-2026-84128

# 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://bugzilla.mozilla.org/show_bug.cgi?id=2044280
https://www.mozilla.org/security/advisories/mfsa2026-82/
https://www.mozilla.org/security/advisories/mfsa2026-86/

Generated by PoC Generator on 2026-09-02T13:20:56.909210007

Frequently asked questions¶

What is CVE-2026-84128?¶

CVE-2026-84128 is a High (8.8) vulnerability: Privilege escalation in the WebDriver BiDi component.. This entry ships a detection-only PoC and a Docker test lab.

How do I detect CVE-2026-84128?¶

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-2026-84128?¶

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.