ConnectWise · ScreenConnect
CVE-2025-3935
ScreenConnect Exposure to ASP.NET ViewState Code Injection
What it is
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.
CISA: ConnectWise ScreenConnect contains an improper authentication vulnerability. This vulnerability could allow a ViewState code injection attack, which could allow remote code execution if machine keys are compromised.
What to do
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Deadline for US federal agencies: June 23, 2025
More exploited flaws from ConnectWise
| Added | Vulnerability | Product | Severity | Attack chance |
|---|---|---|---|---|
| Sep 11, 2026 | Improper Privilege Management and Missing Authorization | ScreenConnect | Critical 9.9 | 0.9% |
| Apr 28, 2026 | Path Traversal | ScreenConnect | High 8.4 | 95% |
| Feb 22, 2024 | Authentication Bypass | ScreenConnect | Critical 10.0 | >99.9% |
Sources: Known Exploited Vulnerabilities (CISA, public domain), CVE records (cve.org) and EPSS (FIRST). The chance of attacks is the EPSS estimate that someone will try to exploit the flaw in the next 30 days.