Actively exploited · Published Apr 25, 2025 · Assigned by ConnectWise
CVE-2025-3935ScreenConnect Exposure to ASP.NET ViewState Code Injection
High 8.1 Exploited
In plain English
A high-severity unsafe deserialization in ScreenConnect from ConnectWise. Attackers are actively exploiting it in the wild (listed by CISA on June 2, 2025). The chance it is exploited in the next 30 days is estimated at 3.6% (higher than 90% of all known vulnerabilities). 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 guidance
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Federal agencies must remediate by Jun 23, 2025.
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| ConnectWise | ScreenConnect | <25.2.3 |
Weakness: CWE-502 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H