CVE-2025-3935 — ScreenConnect versions 25.2.3 and earlier versions may be susceptible to a ViewState code…¶
Key facts
CVE-2025-3935 is a High (8.1) vulnerability: ScreenConnect versions 25.2.3 and earlier versions may be susceptible to a ViewState code…. This entry ships a detection-only PoC and a Docker test lab. It is on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2025-06-02), confirming active exploitation in the wild.
Actively exploited — on the CISA KEV catalog
CVE-2025-3935 is listed on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2025-06-02), confirming exploitation in the wild. Federal remediation deadline: 2025-06-23. Prioritise patching and deploy the detection and prevention rules below.
| CVE | CVE-2025-3935 |
| Severity | High (8.1) |
| CISA KEV | Actively exploited (added 2025-06-02) |
| Detection / prevention | — |
| PoC | poc.py |
| Source | 2025/CVE-2025-3935/ |
Details¶
English | 한국어
Description¶
ScreenConnect versions 25.2.3 and earlier versions may be susceptible to a ViewState code injection attack. ASP.NET Web Forms use ViewState to preserve page and control state, with data encoded using Base64 protected by machine keys. It is important to note that to obtain these machine keys, privileged system level access must be obtained.
If these machine keys are compromised, attackers could create and send a malicious ViewState to the website, potentially leading to remote code execution on the server.
The risk does not originate from a vulnerability introduced by ScreenConnect, but from platform level behavior. This had no direct impact to ScreenConnect Client. ScreenConnect 2025.4 patch disables ViewState and removes any dependency on it.
Vulnerability Details¶
| Property | Value |
|---|---|
| CVE ID | CVE-2025-3935 |
| Type | RCE |
| CVSS Score | 8.1 |
Proof of Concept¶
Download¶
# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2025/CVE-2025-3935/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-2025-3935
# 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://www.connectwise.com/company/trust/advisories
- https://www.connectwise.com/company/trust/security-bulletins/screenconnect-security-patch-2025.4
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-3935
Generated by PoC Generator on 2026-07-29T21:17:11.961362634
Frequently asked questions¶
What is CVE-2025-3935?¶
CVE-2025-3935 is a High (8.1) vulnerability: ScreenConnect versions 25.2.3 and earlier versions may be susceptible to a ViewState code…. This entry ships a detection-only PoC and a Docker test lab. It is on the CISA Known Exploited Vulnerabilities (KEV) catalog (added 2025-06-02), confirming active exploitation in the wild.
How do I detect CVE-2025-3935?¶
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-2025-3935?¶
Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.
Is CVE-2025-3935 actively exploited?¶
Yes. CVE-2025-3935 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, added 2025-06-02, which means it has been exploited in the wild. CISA set a federal remediation deadline of 2025-06-23. Prioritise patching and deploy the detection and prevention rules above.
For authorized security testing and research only. See the full source and NVD record.