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.

Classification

CVE ID: CVE-2025-3935

CVSS Base Severity: HIGH

CVSS Base Score: 8.1

CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected Products

Vendor: ConnectWise

Product: ScreenConnect

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.26% (probability of being exploited)

EPSS Percentile: 49.08% (scored less or equal to compared to others)

EPSS Date: 2025-05-24 (when was this score calculated)

Stakeholder-Specific Vulnerability Categorization (SSVC)

SSVC Exploitation: none

SSVC Technical Impact: total

SSVC Automatable: false

References

https://nvd.nist.gov/vuln/detail/CVE-2025-3935
https://www.connectwise.com/company/trust/security-bulletins/screenconnect-security-patch-2025.4
https://www.connectwise.com/company/trust/advisories

Timeline