CVE-2025-3935
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.
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.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H- connectwise.com/company/trust/advisoriesVendor Advisory
- connectwise.com/company/trust/security-bulletins/screenconnect-security-patch-2025.4Vendor Advisory
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-3935US Government Resource
Actively exploited. Patch immediately.
- Exploitation
- Confirmed in the wild (CISA KEV)
- Federal remediation deadline
- Overdue by 490 days
- CVSS
- 8.1 HIGH
- EPSS (30-day exploit probability)
- 3.6% · top 11% of all CVEs
- Weakness
- CWE-502
- Attack vector
- Network, remotely reachable
- Preconditions
- No privileges and no user interaction
- 1.Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
- 2.Treat as emergency change: patch or isolate internet-facing instances first.
- 3.Review exposure: confirm which instances are reachable from the internet and restrict access until patched.
- 4.Hunt for compromise: review logs for the disclosure window, not just from the patch date.
Assessment is derived automatically from the live signals above; verify against your own asset inventory.