CVE-2025-3935
HIGHCVSS Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
3Description
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.
Analysis
ConnectWise ScreenConnect 25.2.3 and earlier may be susceptible to ViewState code injection when machine keys are compromised, enabling remote code execution through ASP.NET deserialization.
Technical Context
The CWE-502 deserialization vulnerability requires knowledge of the machine keys used for ViewState MAC validation. With the keys, attackers craft serialized .NET payloads signed as valid ViewState data for server-side execution.
Affected Products
['ConnectWise ScreenConnect 25.2.3 and earlier']
Remediation
Update ScreenConnect. Regenerate machine keys. Restrict access to ScreenConnect configuration files. Monitor for unusual ASP.NET deserialization activity.
Priority Score
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External POC / Exploit Code
Leaving vuln.today