# CVE-2025-3935: ConnectWise ScreenConnect Improper Authentication Vulnerability

- Exploited (CISA KEV): yes, added 2025-06-02
- Published: 2025-04-25
- CVSS: 8.1 HIGH (v3.1)
- EPSS: 3.6% (89th percentile)
- CWE: CWE-502

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.

## Edge WAF coverage (claimed by vendors, not measured)

| Vendor | Status | First rule | Days after publication |
|---|---|---|---|
| Cloudflare | No public claim | — | — |
| AWS | No public claim | — | — |
| Microsoft Azure | No public claim | — | — |
| Google Cloud | No public claim | — | — |
| Fastly | Before feed history | — | — |
| F5 | No public claim | — | — |
| Akamai | No public source | — | — |
| OWASP CRS | No public claim | — | — |

"No public claim" means no vendor statement names this CVE; "Before feed history" means the CVE is older than the vendor feed. In both cases generic rules may still block it.

HTML: https://cve.vigilbase.com/cve/CVE-2025-3935 · JSON: https://cve.vigilbase.com/api/v1/cves/CVE-2025-3935