ConnectWise ScreenConnect Improper Authentication Vulnerability
ConnectWise — ScreenConnect
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.
8.1
3.4%
Vector breakdown
- Attack vector
- Network
- Attack complexity
- High
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
- Published
- Apr 25, 2025
- Modified
- Feb 26, 2026
- Added to KEV
- Jun 2, 2025
- Federal patch due
- Jun 23, 2025
CISA required action
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Weakness classification
Proof-of-concept & exploitation references
Weaponization
Public repositories whose name or description references CVE-2025-3935, found via a live GitHub search at request time. These are community-sourced signals, not a verified working exploit — cross-check each one before relying on it, and treat higher star counts and recent activity as (weak) corroboration, not proof.
No public GitHub repositories referencing CVE-2025-3935 were found at last check. Absence here is not proof no exploit exists — see the references below for vendor advisories and write-ups.
References
How this class of flaw gets exploited
Frequently asked questions
What is CVE-2025-3935?
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.
How severe is CVE-2025-3935?
CVE-2025-3935 has a CVSS base score of 8.1 out of 10 (CVSS 3.1).
Is CVE-2025-3935 actively exploited in the wild?
Yes. CVE-2025-3935 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added Jun 2, 2025, meaning CISA has confirmed evidence of active exploitation.
What is the EPSS score for CVE-2025-3935?
3.4% - meaning FIRST.org's EPSS model estimates a 3.4% probability this vulnerability will be exploited in the wild within 30 days (88% percentile among all scored CVEs).
What type of vulnerability is CVE-2025-3935?
CVE-2025-3935 is classified under CWE-502 (CWE-502 Deserialization of Untrusted Data).
Cross-checked against
Impactr finds and proves whether CVE-2025-3935 — or flaws like it — are actually reachable in your own web apps and APIs, with a reproducible exploit as evidence.