Remote code execution via machine-key-forged ViewState
Published Apr 25, 2025 · Updated Feb 26, 2026
ViewState injection in ConnectWise ScreenConnect 25.2.3 and earlier allows remote attackers to execute code through a crafted POST request. The ASP.NET runtime accepts malicious Base64 ViewState as authentic after validating it with compromised instance machine keys, then loads attacker-controlled code into server memory. Reaching the injection path requires prior privileged system-level access to obtain those keys, and successful exploitation compromises the server rather than ScreenConnect clients.
Summary
What happened
ViewState injection in ConnectWise ScreenConnect 25.2.3 and earlier allows remote attackers to execute code through a crafted POST request. The ASP.NET runtime accepts malicious Base64 ViewState as authentic after validating it with compromised instance machine keys, then loads attacker-controlled code into server memory. Reaching the injection path requires prior privileged system-level access to obtain those keys, and successful exploitation compromises the server rather than ScreenConnect clients.
The record
- CVE
- CVE-2025-3935
- Published
- Apr 25, 2025
- Updated
- Feb 26, 2026
- Vendor
- ConnectWise
- Product
- ScreenConnect
- Classifications
- CWE-287, CWE-502, CAPEC-115, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 25, 2025CVE publishedPublication date reported by the CVE source.
- Feb 26, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=<25.2.3
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Reported exploitation
- Nation-state activity affecting ScreenConnect customersthreat actor
- CISA Known Exploited Vulnerabilities listingknown exploited catalog
Technologies
Your stack
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Your stack
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