CVE Intelligence
CISA KEV High Insecure deserialization

CVE-2025-3935 — ConnectWise ScreenConnect Improper Authentication Vulnerability

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.

Published Apr 25, 2025 · Updated Oct 13, 2026 · Sources: CISA Known Exploited Vulnerabilities, NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: ConnectWise

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

CISA KEV · Jun 2, 2025
How the score was calculated
  • Confirmed exploitation (CISA KEV)+35
  • EPSS 3.5% (30-day exploitation probability)+13
  • Technical severity (high)+6

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Confirmed
CISA KEV, listed Jun 2, 2025
EPSS FIRST
3.51%
ahead of 89% of scored CVEs · Oct 14, 2026
Affects
Connectwise
Screenconnect
CVSS base
7.2
High · 4 source(s)
Prioritization reference: 8.1 provisional

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
Active
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Total
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

CISA 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.

US federal deadline: Jun 23, 2025 — passed 479 day(s) ago

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Connectwise Screenconnect).
  2. Treat as emergency remediation: the CVE is in CISA KEV (confirmed exploitation).
  3. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
  4. Search available logs for exploit probes matching the vulnerability class (insecure deserialization), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Connectwise Screenconnect < 25.2.4 Vulnerable NIST National Vulnerability Database
Connectwise Screenconnect version <25.2.3 Vulnerable CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
Low
Privileges required
High
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
8.1 CVSS 3.1 High 2.2 5.9 7d616e1a-3288-43b1-a0dd-0a65d3e70a49 via NIST National Vulnerability Database
8.1 CVSS 3.1 High — — GitHub, Inc. via GitHub Security Advisories
8.1 CVSS 3.1 High — — ConnectWise via CVE Program (cve.org) e CISA ADP
7.2 CVSS 3.1 High 1.2 5.9 nvd@nist.gov via NIST National Vulnerability Database
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H (score shown at the top: nvd@nist.gov)
Scoring entities (NIST, CNA, ADP) score independently; each score is shown with its origin. For prioritization we use 8.1 (7d616e1a-3288-43b1-a0dd-0a65d3e70a49 via NIST National Vulnerability Database) as a conservative provisional reference — not a definitive official score.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-502 · Deserialization of Untrusted Data

Other CVEs with this weakness →

CISA KEV details CISA

CISA lists a CVE once it has evidence of exploitation against real targets.

Listed
Jun 2, 2025
Federal deadline
Jun 23, 2025
passed 479 day(s) ago
Ransomware use
Unknown

CISA records ransomware use only for campaigns it has confirmed, so “Unknown” means unrecorded, not ruled out. The deadline binds US federal agencies; for everyone else it is a reference date.

EPSS over time FIRST

Oct 12, 2026 → Oct 14, 2026 · 3 reading(s) · max 3.51%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
  • Monitor serialized objects in requests and unexpected processes spawned by the runtime.
  • Hunt retroactively in logs from before Jun 2, 2025 (KEV listing): exploitation may have started earlier.
web/proxy/WAF logsnetwork IDS/IPSendpoint telemetry (EDR)application logs

Timeline

What happened to this CVE, newest first.

  • 2026
  • Affected products added · connectwise/screenconnect
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • SSVC assessment updated
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • Affected products added · connectwise/screenconnect
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVSS changed · 7.2
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Analyzed
    Oct 13, 2026 · NIST National Vulnerability Database
  • Added to CISA KEV (detected)
    Oct 13, 2026 · CISA Known Exploited Vulnerabilities
  • Record created in this database
    Oct 13, 2026 · CISA Known Exploited Vulnerabilities
  • 2025
  • Added to CISA KEV catalog
    Jun 1, 2025 · CISA
  • CVE published
    Apr 25, 2025 · ConnectWise

Source activity

Repeated readings are counted rather than listed.

  • 2× References added · Oct 13, 2026 – Oct 13, 2026
  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

5 on the record

Elsewhere on this site

Connectwise
every CVE for this vendor
2025-06
what else CISA listed that month
Insecure deserialization
same class
CWE-502
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-84869 ConnectWise ScreenConnect Improper Privilege Management and Missing Authorization Vulnerability KEV Sep 8, 2026
  • CVE-2026-11596 In ScreenConnect™ versions prior to 26.2, input validation within the Host Pass creation… Jun 10, 2026
  • CVE-2026-3564 ScreenConnect Instance Level Cryptographic Material Exposure Mar 17, 2026
  • CVE-2025-14823 Certificate Signing Extension Returns Encrypted Values Dec 18, 2025
  • CVE-2025-14265 Improper server-side validation in ScreenConnect extension framework Dec 11, 2025
  • CVE-2024-1708 ConnectWise ScreenConnect Path Traversal Vulnerability KEV Feb 21, 2024

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No fixed version, patch or mitigation documented.
  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2025-3935 is "ConnectWise ScreenConnect Improper Authentication Vulnerability", rated High. It affects Screenconnect (Connectwise); versions are in the scope table. It is in CISA KEV: there is evidence of real-world exploitation. CVSS 7.2 describes technical severity. EPSS 3.51% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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