CVE-2025-3935
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.
do firstApply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Can a WAF block it? No. The attack involves sending a malicious ViewState in an HTTP request to the web application. However, the malicious ViewState requires knowledge of machine keys that are only accessible with privileged system access, and the request looks like a normal ViewState payload, so a WAF cannot reliably distinguish malicious from legitimate requests.
Also consider: allow-list classes · patch
Based on an AI reading of the CVE description, and no vendor rule found yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Is CVE-2025-3935 being exploited?
Yes. CVE-2025-3935 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2025-3935?
CVE-2025-3935 is rated High with a CVSS score of 8.1. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2025-3935?
Yes. A fix has been recorded for CVE-2025-3935. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2025-3935 affect?
CVE-2025-3935 affects connectwise:screenconnect. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
- affected< 25.2.3
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.
cisa ssvc
- exploitation
- active
- automatable
- no
- technical impact
- total
Assessed by CISA 6 Jun 2025 (SSVC 2.0.3).
timeline
- 25 Apr 2025Published
- 2 Jun 2025Added to CISA KEV (exploited in the wild) · 37 days later
- 6 Jun 2025CISA SSVC assessment: exploitation active · 4 days later
- 23 Jun 2025CISA remediation due date (US federal agencies) · 17 days later
- 26 Feb 2026CVE record last updated · 249 days (about 8 months) later
- 2 Nov 2026Analysed by vulneraibility.com · 249 days (about 8 months) later
- Linkconnectwise.com /company/trust/security-bulletins/screenconnect-security-patch-2025.4
- Linkconnectwise.com /company/trust/advisories
- Linkcisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-3935
sources
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA KEV catalog: exploitation, date added, due date
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.