CVE-2025-3935: ConnectWise ScreenConnect Improper Authentication Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on , 38 days after the CVE record was published.
- How likely is exploitation in the next 30 days?
- 3.6%
EPSS score, percentile 89.4 of all scored records
- How severe?
- 8.1 High
CVSS v3.1 base score, given by the CNA
- What should I do?
CISA deadline . Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
The CVE record links no vendor advisory, patch or mitigation.
- Which versions are affected?
Affected
- <25.2.3
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of ; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of ; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
What to do
Required action, set by CISA
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
CISA due date for this action: .
Solution (from the CVE record)
Cloud: No action is required. On-premises: Upgrade to the latest stable version. Details and guidance can be found here: ScreenConnect 25.2.4 Security Patch https://www.connectwise.com/company/trust/security-bulletins/screenconnect-security-patch-2025.4
Advisories and patches
The CVE record links no vendor advisory, patch or mitigation.
Linked from CISA's catalog entry
- https://www.connectwise.com/company/trust/security-bulletins/screenconnect-security-patch-2025.4
- https://nvd.nist.gov/vuln/detail/CVE-2025-3935
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | <25.2.3 |
Versions not listed are: unaffected.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
About this vulnerability
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.
Summary: CISA's KEV catalog, as of .
- CISA added CVE-2025-3935 to its Known Exploited Vulnerabilities (KEV) catalog on 2 Jun 2025.
- CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
- The due date CISA sets for the required action is 23 Jun 2025.
- The CVE record was published on 25 Apr 2025, 38 days before it was added to KEV.
- The CVE record carries a CVSS v3.1 base score of 8.1 (High), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 3.6% (percentile 89.4), as of 28 Oct 2026.
- CISA's SSVC assessment in the CVE record: exploitation active, automatable no, technical impact total.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of ; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of ; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of . About the data.
Description
ScreenConnect Exposure to ASP.NET ViewState Code Injection
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.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
Weakness
Attack patterns (CAPEC)
- CAPEC-115: Authentication Bypass
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.
Timeline
| Date | Event |
|---|---|
| CVE record published | |
| Added to CISA KEV | |
| CISA due date for the required action | |
| CVE record last updated |
References
More exploited ConnectWise vulnerabilities
- CVE-2026-84869: ConnectWise ScreenConnect Improper Privilege Management and Missing Authorization Vulnerability
- CVE-2024-1708: ConnectWise ScreenConnect Path Traversal Vulnerability
- CVE-2024-1709: ConnectWise ScreenConnect Authentication Bypass Vulnerability