CVE-2023-47256 Overview
CVE-2023-47256 is an authentication bypass vulnerability in ConnectWise ScreenConnect through version 23.8.4 that allows local users to connect to arbitrary relay servers via implicit trust of proxy settings. This vulnerability stems from improper authentication mechanisms (CWE-287) that fail to validate proxy configurations, potentially enabling attackers to redirect ScreenConnect traffic through malicious relay servers.
Critical Impact
Local attackers can manipulate proxy settings to redirect ScreenConnect connections to attacker-controlled relay servers, potentially compromising the integrity of remote support sessions and enabling man-in-the-middle attacks.
Affected Products
- ConnectWise ScreenConnect through version 23.8.4
- ConnectWise Automate (all versions using vulnerable ScreenConnect components)
Discovery Timeline
- 2024-02-01 - CVE-2023-47256 published to NVD
- 2025-06-17 - Last updated in NVD database
Technical Details for CVE-2023-47256
Vulnerability Analysis
This vulnerability exists in how ConnectWise ScreenConnect handles proxy configuration settings. The application implicitly trusts proxy settings without proper validation, allowing local users to configure the client to connect through arbitrary relay servers. This design flaw bypasses the intended authentication and authorization controls that should restrict which relay servers the client can communicate with.
The root issue lies in the absence of cryptographic verification or whitelist enforcement for relay server connections when proxy settings are modified. An attacker with local access can exploit this trust relationship to intercept, modify, or redirect remote support session traffic.
Root Cause
The vulnerability is caused by improper authentication (CWE-287) in the proxy configuration handling logic. ScreenConnect fails to validate that proxy-directed connections reach legitimate ConnectWise relay infrastructure, creating an authentication bypass condition. The application accepts proxy settings at face value without verifying the integrity or authenticity of the resulting relay server connections.
Attack Vector
The attack requires local access to the system where ScreenConnect client is installed. An attacker can modify proxy settings to redirect the ScreenConnect client's communication through a malicious relay server. This could be achieved through:
The attacker configures local proxy settings or modifies ScreenConnect configuration to point to an attacker-controlled server. When the ScreenConnect client initiates a connection, it implicitly trusts these proxy settings and routes traffic through the malicious relay. This enables the attacker to intercept remote support sessions, potentially capturing credentials or injecting malicious commands.
Detection Methods for CVE-2023-47256
Indicators of Compromise
- Unexpected changes to proxy configurations on endpoints running ScreenConnect
- ScreenConnect client connections to non-standard or unknown relay server addresses
- Modified ScreenConnect configuration files with unauthorized proxy settings
- Network traffic from ScreenConnect processes to IP addresses not associated with ConnectWise infrastructure
Detection Strategies
- Monitor for modifications to ScreenConnect client configuration files
- Implement network-level detection for ScreenConnect traffic destined to non-whitelisted relay servers
- Deploy endpoint detection rules to alert on proxy setting changes affecting remote management tools
- Review authentication logs for anomalous relay server connection patterns
Monitoring Recommendations
- Enable verbose logging for ScreenConnect client connections and proxy usage
- Configure SIEM alerts for configuration file changes in ScreenConnect installation directories
- Establish baseline network behavior for legitimate ScreenConnect relay communications
- Implement application whitelisting for authorized relay server endpoints
How to Mitigate CVE-2023-47256
Immediate Actions Required
- Upgrade ConnectWise ScreenConnect to version 23.8.5 or later immediately
- Audit all ScreenConnect client installations for unauthorized proxy configurations
- Review network logs for any historical connections to unknown relay servers
- Restrict local user permissions to prevent unauthorized configuration changes
Patch Information
ConnectWise has released a security fix in ScreenConnect version 23.8.5 that addresses this vulnerability. Organizations should upgrade all ScreenConnect installations to the latest available version. The official security bulletin is available from ConnectWise Security Bulletins.
For additional technical details about this vulnerability, refer to the Gotham Security analysis.
Workarounds
- Implement strict application control policies to prevent unauthorized proxy configuration changes
- Use network segmentation to restrict ScreenConnect traffic to known ConnectWise relay server IP ranges
- Deploy Group Policy Objects (GPO) to lock down proxy settings on managed endpoints
- Enable endpoint protection monitoring for configuration file integrity on ScreenConnect installations
# Example: Restrict ScreenConnect relay connections via firewall rules
# Allow only legitimate ConnectWise relay server ranges
# Consult ConnectWise documentation for current authorized IP ranges
# Windows Firewall example (PowerShell)
# Block outbound connections from ScreenConnect except to authorized relays
# New-NetFirewallRule -DisplayName "ScreenConnect Relay Whitelist" -Direction Outbound -Program "C:\Program Files (x86)\ScreenConnect Client\ScreenConnect.ClientService.exe" -RemoteAddress <authorized-relay-ips> -Action Allow
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
