CVE-2026-3564Network attack vector

Elevated access via forged session authentication values

Published Mar 17, 2026 · Updated Mar 17, 2026

Improper signature verification in ConnectWise ScreenConnect servers before 26.1 allows remote attackers to gain unauthorized elevated access. Disclosed ASP.NET machine keys let attackers forge or modify framework-protected session values that the server accepts as authentic. Exploitation requires access to an instance's server-level cryptographic material and enables unauthorized actions, including entry to active sessions.

CVSS severity9.0
Critical
EPSS probability0.36%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper signature verification in ConnectWise ScreenConnect servers before 26.1 allows remote attackers to gain unauthorized elevated access. Disclosed ASP.NET machine keys let attackers forge or modify framework-protected session values that the server accepts as authentic. Exploitation requires access to an instance's server-level cryptographic material and enables unauthorized actions, including entry to active sessions.

The record

CVE
CVE-2026-3564
Published
Mar 17, 2026
Updated
Mar 17, 2026
Vendor
ConnectWise
Product
ScreenConnect
Classifications
CWE-347, T1606.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 17, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 17, 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.

  1. Affected versionversion=All versions prior to 26.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ConnectWise · ScreenConnectversion=All versions prior to 26.1

Published CVSS scores

9.0ConnectWiseCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-347Improper Verification of Cryptographic Signature
T1606.001Forge Web Credentials: Web Cookies

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.

Technologies

Your stack

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Your stack

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