CVE-2026-103647 — Cross-site scripting in the webmail of Progressive Robot hMailServer 6.3.2 through 6.3.5…¶

Key facts

CVE-2026-103647 is a High (8.0) vulnerability: Cross-site scripting in the webmail of Progressive Robot hMailServer 6.3.2 through 6.3.5…. This entry ships a detection-only PoC and a Docker test lab.


CVE	CVE-2026-103647
Severity	High (8.0)
Detection / prevention	—
PoC	poc.py
Source	2026/CVE-2026-103647/

Details¶

English | 한국어

Description¶

Cross-site scripting in the webmail of Progressive Robot hMailServer 6.3.2 through 6.3.5 allows a remote attacker who can send a user an encrypted message to run script in the webmail's origin with that user's session. When the webmail decrypted an S/MIME message (from 6.3.2) or an OpenPGP message (from 6.3.4) in the browser, it offered each decrypted attachment as a blob URL of the media type the message declared for it. A click saved the file, but if the user opened the attachment in a new tab, a part declared as text/html was rendered as a document of the webmail's origin and its script could read the mailbox, send mail and change the account through the REST API. The webmail is served only when the REST API is enabled, which it is not by default.

Vulnerability Details¶

Property	Value
CVE ID	CVE-2026-103647
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-2026-103647/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-2026-103647

# 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://gitlab.com/hmailserver/hmailserver/-/releases/v6.3.6
https://gitlab.com/hmailserver/hmailserver/-/work_items/52

Generated by PoC Generator on 2026-10-08T21:13:13.390248797

Frequently asked questions¶

What is CVE-2026-103647?¶

CVE-2026-103647 is a High (8.0) vulnerability: Cross-site scripting in the webmail of Progressive Robot hMailServer 6.3.2 through 6.3.5…. This entry ships a detection-only PoC and a Docker test lab.

How do I detect CVE-2026-103647?¶

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-2026-103647?¶

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.