Deserialization in Connectwise Screenconnect
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.
Vulnerability class: Insecure Deserialization
EPSS: 0.034 (88.0th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.
Affected products
- Connectwise Screenconnect — versions <25.2.3
Weakness classification (CWE)
CISA KEV (Known Exploited Vulnerabilities)
This CVE is on the CISA KEV catalog, added on . CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.
BOD 22-01 due date: .
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.
Public proof-of-concept exploits
References
- 7d616e1a-3288-43b1-a0dd-0a65d3e70a49 (Vendor Advisory)
- 7d616e1a-3288-43b1-a0dd-0a65d3e70a49 (Vendor Advisory)
- 134c704f-9b21-4f2e-91b3-4a467353bcc0 (US Government Resource)
Frequently asked questions
- What is CVE-2025-3935?
- CVE-2025-3935 is a high-severity vulnerability in Connectwise Screenconnect, classified under Deserialization of Untrusted Data. CVSS score: 8.1/10. Published 2025-04-25.
- How severe is CVE-2025-3935?
- High severity. CVSS v3 base score is 8.1 out of 10.
- Is CVE-2025-3935 known to be exploited?
- Yes. CVE-2025-3935 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2025-06-02), indicating it is being actively exploited. 3 public proof-of-concept repositories are indexed.