CVE-2026-54617 — GravitLauncher is an open-source Minecraft launcher based on sashok724's v3.¶
Key facts
CVE-2026-54617 is a Critical (9.8) vulnerability: GravitLauncher is an open-source Minecraft launcher based on sashok724's v3.. This entry ships a detection-only PoC and a Docker test lab.
| CVE | CVE-2026-54617 |
| Severity | Critical (9.8) |
| Detection / prevention | — |
| PoC | poc.py |
| Source | 2026/CVE-2026-54617/ |
Details¶
English | 한국어
Description¶
GravitLauncher is an open-source Minecraft launcher based on sashok724's v3. Prior to 5.7.12, an unauthenticated remote actor can send a raw HTTP request target without a leading slash to the default LaunchServer file server on port 9274. FileServerHandler.channelRead0 in components/launchserver/src/main/java/pro/gravit/launchserver/socket/handlers/fileserver/FileServerHandler.java strips the first request-target character and resolves the remaining path against updatesDir without re-normalizing and verifying containment. This leaves parent-directory components in a no-leading-slash request and allows reading any file accessible to the LaunchServer process, including .keys/ecdsa_id, .keys/legacySalt, and LaunchServer.json. Disclosure of those files can expose signing keys, refresh-token material, and database credentials, enabling forged administrative access tokens and full authentication bypass. A normalizing L7 proxy may block the primary request form, but direct exposure and L4/TCP proxies remain affected, and netty.fileServerEnabled is enabled by default. This issue is fixed in 5.7.12.
Vulnerability Details¶
| Property | Value |
|---|---|
| CVE ID | CVE-2026-54617 |
| Type | RCE |
| CVSS Score | 9.8 |
Proof of Concept¶
Download¶
# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2026/CVE-2026-54617/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-2026-54617
# 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/GravitLauncher/Launcher/commit/8114a1d4cfbcaab4c1c337d921597805d71dee3b
- https://github.com/GravitLauncher/Launcher/releases/tag/v5.7.12
- https://github.com/GravitLauncher/Launcher/security/advisories/GHSA-5g75-477j-2c2f
Generated by PoC Generator on 2026-09-18T05:15:03.398937243
Frequently asked questions¶
What is CVE-2026-54617?¶
CVE-2026-54617 is a Critical (9.8) vulnerability: GravitLauncher is an open-source Minecraft launcher based on sashok724's v3.. This entry ships a detection-only PoC and a Docker test lab.
How do I detect CVE-2026-54617?¶
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-2026-54617?¶
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.