CyberSecBulletin
CVE-2026-3564NVD status: Awaiting Analysis

ScreenConnect: Improper Verification of Cryptographic Signature

Published Updated By the CyberSecBulletin desk

CVE-2026-3564 is a critical-severity improper verification of cryptographic signature vulnerability in ScreenConnect from ConnectWise, with a CVSS 3.1 base score of 9.0 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected ScreenConnect versions: All server versions prior to 26.1. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.4% chance of exploitation within 30 days, which is low compared with other CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Check which version of ScreenConnect you run against the affected versions below, and install the vendor's latest release.
  2. Read the advisory on connectwise.com for workarounds and exact fixed builds.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
ConnectWiseScreenConnectAll server versions prior to 26.1Not stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
HighSuccess depends on conditions outside the attacker's control.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
ChangedThe attack can reach beyond the vulnerable component into other systems.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H. Scored by CNA.

Official description

A condition in the ScreenConnect server component may allow an actor with access to server-level cryptographic material used for authentication to obtain unauthorized access, including elevated privileges, in certain scenarios. ScreenConnect host and guest client agents are not independently affected by this CVE.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Verification of Cryptographic Signature

The product does not verify, or incorrectly verifies, the cryptographic signature for data.

More Improper Verification of Cryptographic Signature vulnerabilities (CWE-347)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in ScreenConnect

All ScreenConnect vulnerabilities

Recent Improper Verification of Cryptographic Signature vulnerabilities

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