Overview
The cybersecurity landscape is ever-evolving with new vulnerabilities surfacing frequently. One such vulnerability is the CVE-2025-3935, which affects ScreenConnect versions 25.2.3 and earlier. This vulnerability arises from an issue with ViewState, a feature used by ASP.NET Web Forms to preserve state information. If exploited, this vulnerability could lead to potential system compromise or data leakage, underlining its significance in terms of cybersecurity.
Vulnerability Summary
CVE ID: CVE-2025-3935
Severity: High (8.1 CVSS Score)
Attack Vector: Network
Privileges Required: High (System level access)
User Interaction: None
Impact: Potential system compromise or data leakage
Affected Products
No phone number, email, or personal info required.
Product | Affected Versions
ScreenConnect | 25.2.3 and earlier versions
How the Exploit Works
The exploit works by taking advantage of ViewState, a feature in ASP.NET Web Forms. ViewState preserves page and control states, encoding data using Base64 and protecting it with machine keys. If an attacker gains access to these machine keys, they could create a malicious ViewState and send it to the website. This potentially leads to remote code execution on the server, hence compromising the system or leading to data leakage.
Conceptual Example Code
A conceptual example of how this vulnerability might be exploited could be an HTTP request like the one below, where the attacker injects a malicious ViewState:
POST /target/endpoint HTTP/1.1
Host: target.example.com
Content-Type: application/x-www-form-urlencoded
__VIEWSTATE=<malicious ViewState here>Note that this is purely conceptual and would require the attacker to have already obtained the necessary machine keys to create a malicious ViewState.
Mitigation
The vendor has released a patch (ScreenConnect 2025.4) that disables ViewState, thus remedying the vulnerability. Users are urged to apply this patch as soon as possible. In the interim, a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can be used for temporary mitigation. Security teams should also ensure that system level access is strictly controlled and monitored to prevent unauthorized access.