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CVE-2025-3935

ConnectWise ScreenConnect Improper Authentication

8.1 HIGHActively exploited (CISA KEV)EPSS 3.51%
  1. Published25 Apr 2025
  2. Added to CISA KEV2 Jun 2025
  3. Remediation due23 Jun 2025
Actively exploited (CISA KEV)

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.

Added to KEV: 2 Jun 2025Federal remediation due: 23 Jun 2025

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityHigh
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

ConnectWise Screenconnect< 25.2.4

Remediation

Fixed in
ConnectWise Screenconnect≥ 25.2.4

References

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Frequently asked

Is CVE-2025-3935 being actively exploited?

Yes. CVE-2025-3935 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 2 Jun 2025.

How severe is CVE-2025-3935?

CVE-2025-3935 has a CVSS 3.1 base score of 8.1, rated high. EPSS estimates a 3.51% probability of exploitation.

Which products are affected by CVE-2025-3935?

Affected products include ConnectWise Screenconnect.

How do I fix CVE-2025-3935?

Upgrade affected software to a fixed version, for example ConnectWise Screenconnect 25.2.4 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2025-3935 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, a risk for it never ranks below high, and the update that fixes it moves to the Emergency patch lane. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.