CVE-2025-3935 ConnectWise ScreenConnect Improper Authentication
Attackers with privileged access to machine keys can inject malicious ViewState data to achieve remote code execution on the server.
- Exploited in the wild
- Since 2 Jun 2025
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2025-3935?
CVE-2025-3935 is a high-severity unsafe deserialization vulnerability in ConnectWise ScreenConnect, published on 25 Apr 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-502
Which versions are affected by CVE-2025-3935?
It affects 1 product.
Products include Connectwise Screenconnect.
How do I fix CVE-2025-3935?
No fix has been published for CVE-2025-3935 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 23 Jun 2025.
Upgrade, and only deserialise data from trusted sources or with an allow-list of types. More about Unsafe deserialization.
Is CVE-2025-3935 being exploited?
Yes. Attackers have exploited CVE-2025-3935 in the wild since at least 2 Jun 2025.
Other vulnerabilities in ConnectWise ScreenConnect
- CVE-2024-1709 ConnectWise ScreenConnect Authentication Bypass
- CVE-2026-84869 ConnectWise ScreenConnect Improper Privilege Management and Missing Authorization
- CVE-2024-1708 ConnectWise ScreenConnect Path Traversal
- CVE-2025-14265 Improper server-side validation in ScreenConnect extension framework
- CVE-2025-14823 Certificate Signing Extension Returns Encrypted Values
Sources
Also known as GHSA-qjrp-xr9r-wmrg.