CVE-2025-3935: ConnectWise ScreenConnect Improper Authentication Vulnerability

CISA Known Exploited Vulnerabilities

Name

ConnectWise ScreenConnect Improper Authentication Vulnerability

Vendor

ConnectWise

Product

ScreenConnect

Added to the catalog

2025-06-02

Due date for US federal agencies

2025-06-23

Weaknesses

CWE-287

Catalog version

2026.10.30

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.

Required action (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.

Ransomware use: CISA does not mark known use of this vulnerability in ransomware campaigns.

Links in CISA's notes

• https://www.connectwise.com/company/trust/security-bulletins/screenconnect-security-patch-2025.4
• https://nvd.nist.gov/vuln/detail/CVE-2025-3935

Read on 2026-11-02T23:39:54.475Z under licence cisa-kev-cc0@b0067899 from https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json

NVD analysis

Status

Analyzed

Published

2025-04-25T19:15:49.143

Last modified

2026-06-17T09:20:57.337

Weaknesses

CWE-502

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.

References

• 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)

This product uses the NVD API but is not endorsed or certified by the NVD.

Read on 2026-11-02T23:42:22.836Z under licence nvd-api-terms-of-use@ff2a5288 from https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2025-3935

CVE record

Title (CNA)

ScreenConnect Exposure to ASP.NET ViewState Code Injection

Assigner

ConnectWise

State

PUBLISHED

Published

2025-04-25T18:27:44.244Z

Updated

2026-02-26T18:28:01.567Z

Problem types

CWE-502 Deserialization of Untrusted Data

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.

References

• https://www.connectwise.com/company/trust/security-bulletins/screenconnect-security-patch-2025.4
• https://www.connectwise.com/company/trust/advisories

Read on 2026-11-03T02:16:24.482Z under licence cve-terms-of-use@81bfa2f3 from https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2025/3xxx/CVE-2025-3935.json

Defensive techniques (MITRE D3FEND)

D3FEND maps these defensive techniques to the weakness (CWE) that NVD lists for this CVE, through the digital artifacts the weakness affects. D3FEND does not say they stop this vulnerability.

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