CVE-2025-3935
ScreenConnect Exposure to ASP.NET ViewState Code Injection
ConnectWise ScreenConnect Improper Authentication Vulnerability is confirmed as actively exploited and is listed in the CISA KEV catalog.
Required action
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
CISA notes
https://www.connectwise.com/company/trust/security-bulletins/screenconnect-security-patch-2025.4 ; https://nvd.nist.gov/vuln/detail/CVE-2025-3935
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.
Severity
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:HAffected Products
| Vendor | Product | Affected versions |
|---|---|---|
| ConnectWise | ScreenConnect | <25.2.3 |
References
2 LinksRecord Details
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