ConnectWise ScreenConnect client file-transfer authorization flaw, worm-like exploitation from 20 August 2026, patched 26.6.5

Adversaries may create or modify Windows services to repeatedly execute malicious payloads as part of persistence. When Windows boots up, it starts programs or applications called services that perform background system functions. Windows service configuration information, including the file path to the service's executable or recovery programs/commands, is stored in the Windows Registry.

Evidence: 2026-09-12/cve-2026-84869-connectwise-screenconnect-worm-file-transfer · ATT&CK page ↗

Adversaries may create or modify Windows services to repeatedly execute malicious payloads as part of persistence. When Windows boots up, it starts programs or applications called services that perform background system functions. Windows service configuration information, including the file path to the service's executable or recovery programs/commands, is stored in the Windows Registry.

Evidence: 2026-09-12/cve-2026-84869-connectwise-screenconnect-worm-file-transfer · ATT&CK page ↗

Adversaries may bypass UAC mechanisms to elevate process privileges on system. Windows User Account Control (UAC) allows a program to elevate its privileges (tracked as integrity levels ranging from low to high) to perform a task under administrator-level permissions, possibly by prompting the user for confirmation. The impact to the user ranges from denying the operation under high enforcement to allowing the user to perform the action if they are in the local administrators group and click through the prompt or allowing them to enter an administrator password to complete the action.

Evidence: 2026-09-12/cve-2026-84869-connectwise-screenconnect-worm-file-transfer · ATT&CK page ↗

Adversaries may exploit vulnerabilities to evade detection by hiding activity, suppressing logging, or operating within trusted or unmonitored components.

Evidence: 2026-09-12/cve-2026-84869-connectwise-screenconnect-worm-file-transfer · ATT&CK page ↗

Adversaries may disable, degrade, or tamper with security tools or applications (e.g., endpoint detection and response (EDR) tools, intrusion detection systems (IDS), antivirus, logging agents, sensors, etc.) to impair or reduce visibility of defensive capabilities. This may include stopping specific services, killing processes, modifying or deleting tool configuration files and Registry keys, or preventing tools from updating. This may also include impairing defenses more broadly by disrupting preventative, detection, and response mechanisms across host, network, and cloud environments.

Evidence: 2026-09-12/cve-2026-84869-connectwise-screenconnect-worm-file-transfer · ATT&CK page ↗

Adversaries may transfer tools or other files between systems in a compromised environment. Once brought into the victim environment (i.e., Ingress Tool Transfer) files may then be copied from one system to another to stage adversary tools or other files over the course of an operation.

Evidence: 2026-09-12/cve-2026-84869-connectwise-screenconnect-worm-file-transfer · ATT&CK page ↗

Adversaries may use a connection proxy to direct network traffic between systems or act as an intermediary for network communications to a command and control server to avoid direct connections to their infrastructure. Many tools exist that enable traffic redirection through proxies or port redirection, including HTRAN, ZXProxy, and ZXPortMap. Adversaries use these types of proxies to manage command and control communications, reduce the number of simultaneous outbound network connections, provide resiliency in the face of connection loss, or to ride over existing trusted communications paths between victims to avoid suspicion. Adversaries may chain together multiple proxies to further disguise the source of malicious traffic.

Evidence: 2026-09-12/cve-2026-84869-connectwise-screenconnect-worm-file-transfer · ATT&CK page ↗

Adversaries may transfer tools or other files from an external system into a compromised environment. Tools or files may be copied from an external adversary-controlled system to the victim network through the command and control channel or through alternate protocols such as ftp. Once present, adversaries may also transfer/spread tools between victim devices within a compromised environment (i.e. Lateral Tool Transfer).

Evidence: 2026-09-12/cve-2026-84869-connectwise-screenconnect-worm-file-transfer · ATT&CK page ↗

An adversary may use legitimate remote access tools to establish an interactive command and control channel within a network. Remote access tools create a session between two trusted hosts through a graphical interface, a command line interaction, a protocol tunnel via development or management software, or hardware-level access such as KVM (Keyboard, Video, Mouse) over IP solutions. Desktop support software (usually graphical interface) and remote management software (typically command line interface) allow a user to control a computer remotely as if they are a local user inheriting the user or software permissions. This software is commonly used for troubleshooting, software installation, and system management. Adversaries may similarly abuse response features included in EDR and other defensive tools that enable remote access.

Evidence: 2026-09-12/cve-2026-84869-connectwise-screenconnect-worm-file-transfer · ATT&CK page ↗

Adversaries may leverage the resources of co-opted systems to complete resource-intensive tasks, which may impact system and/or hosted service availability.

Evidence: 2026-09-12/cve-2026-84869-connectwise-screenconnect-worm-file-transfer · ATT&CK page ↗