ScreenConnect versions 25.2.3 and earlier versions may be susceptible to a ViewState code injection attack
Why It Matters
Analysis dossierWhy It Matters
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.
Immediate Attention
Yes
Unknown
Risk basis: CISA KEV exploitation signal; HIGH severity; Known exploitation signal from CISA KEV or ransomware metadata; Source-confirmed exploitation or CISA KEV/ransomware metadata
Affected Products & Remediation
1 source-backed product- connectwise screenconnect · < 25.2.4 · NVD CPE · Source
Vendor or catalog guidance (source)
- CISA KEV: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Known exploitation (source facts)
Only what a source states. Unknown means no source has said either way; it is not "not exploited".
- CISA KEV
- Listed
- Exploited (source statement)
- Yes
- Publicly disclosed (source)
- Unknown
CISA 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.
Suggested hunting (rule-based inference)
SecOps Signal recommendation (rule-based inference). These steps are hunting hypotheses from the vulnerability class; they do not state or imply that exploitation occurred here or anywhere.
Matched kev-network-exposure (CVSS AV:N, CISA KEV Listed); deserialization (CWE-502)
Exposure
- Identify assets with the exact CVE and confirm the affected product/version against the advisory.Telemetry: DeviceTvmSoftwareVulnerabilities · KEV listing raises urgency, but inventory is needed to establish local exposure. · Rule kev-network-exposure
- Find installations of the affected component and confirm the source-stated version range.Telemetry: Application inventory · Deserialization risk requires component and version evidence. · Rule deserialization
Exploitation evidence
- Review relevant edge or application access logs for unusual requests around the advisory window.Telemetry: CommonSecurityLog · Log review is a hunting hypothesis; KEV listing alone does not show local exploitation. · Rule kev-network-exposure
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Exploitation evidence
- Review unusual child processes or network connections from the affected service.Telemetry: DeviceProcessEvents · Unexpected behavior may support investigation but is not proof by itself. · Rule deserialization
Response
- Recheck the affected assets after the source-stated mitigation or update is applied.Telemetry: DeviceTvmSoftwareVulnerabilities · A follow-up inventory check verifies local remediation. · Rule kev-network-exposure
CISA KEV Record
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Change History & Source Data
— No recorded material change
- CNA / source
- 7d616e1a-3288-43b1-a0dd-0a65d3e70a49
- Record status · verification
- UPDATED · CISA KEV confirmed
- CPE
- cpe:2.3:a:connectwise:screenconnect:*:*:*:*:*:*:*:*
Evidence & Provenance
Linked by the query's stored exact CVE association. Review required tables and validation status before use.
DeviceTvmSoftwareVulnerabilities| where CveId == "CVE-2025-3935"| project DeviceId, DeviceName, OSPlatform, OSVersion, SoftwareVendor, SoftwareName, SoftwareVersion, CveId, VulnerabilitySeverityLevel, RecommendedSecurityUpdate, RecommendedSecurityUpdateId| sort by VulnerabilitySeverityLevel descLooking up related community queries…