CVEs / CVE-2025-3935
CVE-2025-3935: ConnectWise ScreenConnect Improper Authentication Vulnerability
- Known exploited in the CISA KEV catalog since 2 Jun 2025
- high 7.2 CVSS 3.1 (NVD)
- EPSS 3.59% chance of exploitation in the next 30 days, higher than 89% of CVEs (30 Oct 2026)
- Last changed at its sources
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Summary
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.
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 and fixed versions
| Product | Affected | Fixed in |
|---|---|---|
| ConnectWise ScreenConnect | <25.2.3 | — |
Exploitation
| In CISA KEV since | 2 Jun 2025 |
|---|---|
| Due date for US federal agencies | 23 Jun 2025 |
| Used in ransomware campaigns | Unknown |
| 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. |
Severity
| CVSS 3.1 | 7.2 highCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:HScored by NVD |
|---|---|
| Weakness | CWE-502 |
References
- CVE-2025-3935 on NVD
- CVE-2025-3935 in the CISA KEV catalog
- https://www.connectwise.com/company/trust/security-bulletins/screenconnect-security-patch-2025.4 (cited by CISA)
- https://www.connectwise.com/company/trust/advisories Vendor Advisory
- https://www.connectwise.com/company/trust/security-bulletins/screenconnect-security-patch-2025.4 Vendor Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-3935 US Government Resource
Sources
Exploitation status from the CISA Known Exploited Vulnerabilities catalog. EPSS scores from FIRST. Descriptions, severity and references from the National Vulnerability Database. Open-source package versions from OSV (CC-BY 4.0). Text is shown as each source states it; Stackurity does not edit it. Check the vendor's advisory before acting.
This product uses data from the NVD API but is not endorsed or certified by the NVD.