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Screenconnect EUVDEUVD-2026-12574

| CVE-2026-3564 CRITICAL
Improper Verification of Cryptographic Signature (CWE-347)
2026-03-17 ConnectWise
9.0
CVSS 3.1 · Vendor: ConnectWise
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Obtain server-level cryptographic material
  2. Delivery
    Forge authentication credentials
  3. Exploit
    Bypass ScreenConnect authentication
  4. Execution
    Escalate privileges
  5. Impact
    Execute unauthorized actions with elevated access

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A04:2025 - Cryptographic Failures
ASVS 5.0
V11 - Cryptography Signature verification
Exploitation Conditions

Attacker must possess access to ScreenConnect server-level cryptographic material used for authentication. This requires prior compromise of server secrets or insider access to key management systems.

Impact

Despite the critical CVSS score of 9.0, the actual exploitation risk requires careful analysis. The CVSS vector (AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H) indicates network-accessible attack with high complexity but no privileges or user interaction required, with scope change and complete compromise of confidentiality, integrity, and availability. The high attack complexity suggests exploitation requires obtaining server-level cryptographic material first, which significantly limits the attacker pool. No EPSS score is provided to indicate real-world exploitation probability, and the vulnerability is not listed in CISA's Known Exploited Vulnerabilities catalog, suggesting no observed in-the-wild exploitation. However, the authentication bypass nature and potential for complete system takeover make this a priority for organizations using ScreenConnect, especially those with higher exposure to sophisticated threat actors.

Exploit ScenarioDerived

An attacker who compromises a ScreenConnect server through other means or obtains cryptographic key material via insider threat or supply chain attack could forge authentication tokens to impersonate any user, including administrators. Once authenticated with elevated privileges, the attacker gains full control over all managed endpoints connected to the ScreenConnect instance, potentially compromising an entire enterprise fleet of systems. The high attack complexity in the CVSS score suggests this scenario requires significant technical sophistication or prior access to cryptographic materials.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.
No patch listed yet 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 17, 2026

A cryptographic authentication bypass vulnerability in ConnectWise ScreenConnect allows remote attackers who gain access to server-level cryptographic material to authenticate as any user and obtain elevated privileges. The vulnerability affects all ScreenConnect versions prior to 26.1 and carries a CVSS score of 9.0, indicating critical severity. While not currently listed in CISA's KEV catalog and with no public proof-of-concept available, the vulnerability's authentication bypass nature and potential for complete system compromise make it a high-priority patching target.

RemediationAI

Upgrade ConnectWise ScreenConnect to version 26.1 or later immediately, as detailed in the vendor security bulletin at https://www.connectwise.com/company/trust/security-bulletins/2026-03-17-screenconnect-bulletin. Until patching is complete, organizations should audit and rotate all server-level cryptographic keys and certificates, implement network segmentation to limit ScreenConnect server exposure, enable comprehensive logging for authentication events, and monitor for suspicious authentication patterns or privilege escalations. Additional information is available from the VulDB advisory at https://vuldb.com/?id.351372.

Affected VersionsENISA

ScreenConnect All versions prior to 26.1

Affected Packages

euvd screenconnect_all_versions_prior_to no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

ConnectWise ScreenConnect (CPE: cpe:2.3:a:connectwise:screenconnect:*:*:*:*:*:*:*:*) is a remote desktop and support software solution that relies on cryptographic authentication mechanisms to verify user identities. The vulnerability is classified as CWE-347 (Improper Verification of Cryptographic Signature), indicating that the application fails to properly validate cryptographic signatures or tokens used for authentication. Based on the tags mentioning 'JWT Attack', this likely involves JSON Web Token authentication where the server accepts tokens signed with compromised or improperly validated cryptographic keys, allowing attackers to forge authentication credentials.

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Severity by source

Vendor (ConnectWise) PRIMARY 9.0 CRITICAL
AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

Primary rating from Vendor (ConnectWise) · only source for this CVE.

CVSS VectorVendor: ConnectWise

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

DescriptionCVE.org

A condition in ScreenConnect may allow an actor with access to server-level cryptographic material used for authentication to obtain unauthorized access, including elevated privileges, in certain scenarios.

Executive ViewAI

Why It Matters

A critical authentication bypass vulnerability in ConnectWise ScreenConnect (CVE-2026-3564, CVSS 9.0) enables attackers with access to cryptographic keys to impersonate any user and gain system administrator privileges, potentially compromising all data and systems managed through affected ScreenConnect instances. Organizations using ScreenConnect versions prior to 26.1 face imminent risk of complete remote access compromise with no available patch, requiring immediate mitigation to prevent unauthorized administrative access.

Business Impact: Severe
Compensating Controls

Implement strict network segmentation and firewall rules limiting ScreenConnect access to trusted IP ranges only; enforce multi-factor authentication for all ScreenConnect user accounts; disable or restrict remote access features not actively in use; implement web application firewall (WAF) rules to monitor and alert on suspicious authentication patterns; increase monitoring and alerting on administrative account activity and privilege escalations; establish air-gapped backup recovery procedures independent of ScreenConnect infrastructure; continuously monitor vendor advisories for patch availability.

Threat Intelligence Overview

EPSS Score
0.0%
Top 86% exploitable
Data Quality
5 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity CRITICAL
CISA KEV No
Public POC No
EPSS 0.0%
Patch available No
Active threat No
Deciding rule
CRITICAL severity
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
No
Human Impact
Very High

Priority Score

45
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +45
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

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