What’s Vulnerable › Vulnerabilities

CVE-2025-3935: ConnectWise ScreenConnect Improper Authentication Vulnerability

• Severity: high (CVSS 7.2 v3.1)
• Exploited in the wild: yes — in CISA KEV since 2025-06-02
• EPSS: 3.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-04-25 · updated 2026-06-17
• Weakness: CWE-502

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

• ConnectWise ScreenConnect: before 25.2.4 — fixed in 25.2.4

How to fix

Upgrade to a fixed version: ConnectWise ScreenConnect 25.2.4. Check the vendor advisory for mitigations.

References

• https://www.connectwise.com/company/trust/advisories
• https://www.connectwise.com/company/trust/security-bulletins/screenconnect-security-patch-2025.4
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-3935

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