Vulnerability Summary
- Vulnerability Name: ConnectWise ScreenConnect Code Integrity Bypass
- CVE ID: CVE-2025-14265
- CVSS Score: 9.1
- Severity: Critical
- CWE: CWE-494 (Download of Code Without Integrity Check)
- Attack Vector: Network
- Attack Complexity: Low
- Privileges Required: High (Administrative or Authorized User)
- User Interaction: None
- Scope: Changed
- Impact: High impact to confidentiality, integrity, and availability
- Exploit Status: No confirmed exploitation or public PoC at disclosure
- Patch Available: Yes
Overview
ConnectWise has disclosed and fixed a critical security flaw in the ScreenConnect server that could allow trusted users or compromised administrators to install and execute unverified or malicious extensions. The issue, tracked as CVE-2025-14265, affects all ScreenConnect server versions prior to 25.8 and was publicly disclosed on December 11, 2025.
The vulnerability does not affect guest or host clients. It is limited to the server component, which makes it especially important for self-hosted and MSP environments, where the ScreenConnect server often has broad access to customer systems.
What Caused the Issue
The problem exists in ScreenConnect’s extension subsystem. The server did not properly validate the authenticity or integrity of extension packages before installing and executing them.
In practical terms, this means:
- Extension code could be downloaded and run
- No strong server-side integrity checks were enforced
- The system trusted extension content without confirming it was safe
This behavior falls under CWE-494, a well-known class of supply-chain and insider-threat vulnerabilities.
How the Vulnerability Can Be Abused
Exploitation requires high-level access, such as:
- An administrative account
- An authorized user account with extension privileges
If an attacker gains such access (through credential theft, phishing, or insider misuse), exploitation is straightforward:
- A malicious extension is uploaded
- The server installs and executes it without validation
- The attacker gains persistent code execution
No additional user interaction is required once credentials are compromised.
Impact and Risk
If exploited, CVE-2025-14265 can lead to severe outcomes:
Remote Code Execution
Attackers can execute arbitrary code on the ScreenConnect server, potentially gaining full control of the host system.
Exposure of Sensitive Data
Configuration files may expose credentials, API keys, encryption secrets, and internal system details.
Platform Trust Breakdown
Malicious extensions can create backdoors, undermine server integrity, and persist across restarts.
Lateral Movement
Because ScreenConnect often manages access to thousands of endpoints, a compromised server can be used to move laterally into customer or internal environments.
The CVSS score of 9.1 reflects the seriousness of these risks, even though exploitation requires elevated access.
Affected Software
- ScreenConnect Server – all versions prior to 25.8
- Not affected: ScreenConnect host and guest clients
The risk is highest for:
- On-premises deployments
- MSP environments
- Servers with multiple administrators
Official Patch and Fixed Version
ConnectWise has released ScreenConnect version 25.8, which fully addresses CVE-2025-14265.
What the Patch Does
- Enforces server-side validation for extensions
- Adds integrity checks before extension installation
- Prevents execution of untrusted extension code
Official Patch Reference
- Security Bulletin:
https://www.connectwise.com/company/trust/security-bulletins/screenconnect-2025.8-security-patch - Download Page:
https://www.screenconnect.com/download
Remediation by Deployment Type
Cloud-Hosted ScreenConnect
- No action required
- ConnectWise has already applied the patch automatically
On-Premises ScreenConnect
- Immediate action required
- Administrators must manually upgrade to version 25.8
Automate-Integrated Deployments
- Update the Automate ScreenConnect extension first
- Ensure extension version 4.4.0.16 or later
- Then upgrade the ScreenConnect server to 25.8
Upgrade Preparation (On-Premises)
Before upgrading:
- Confirm license is active and under maintenance
- Check current version (Administration > About or version.txt)
- Review required upgrade path if running very old versions
- Back up:
- Entire ScreenConnect installation directory
- ScreenConnect database file
Upgrade Process
- Download ScreenConnect 25.8
- Schedule downtime and notify users
- Run the installer as Administrator
- Allow automatic service stop, upgrade, and restart
- Verify version shows 25.8 or later
- Update guest clients after server upgrade
Post-Upgrade Validation
After upgrading:
- Confirm server version
- Test remote sessions
- Verify audit logging
- Confirm extensions behave correctly
- Review installed extensions and remove anything unknown
Extension Auditing and Review
Web Interface (Primary Method)
- Administration → Extensions → Installed
- Review name, version, author, and install date
File System Review (On-Premises)
- Review
App_Extensionsdirectory - Check timestamps and unexpected files
Database Review (On-Premises)
- Inspect
ScreenConnect.dbfor extension records - Validate against known, approved extensions
Additional Security Recommendations
- Limit administrative accounts to essential staff only
- Enable MFA for all admin users
- Monitor audit logs for extension activity
- Regularly review and remove unused extensions
- Restrict network access to admin interfaces
Current Exploitation Status
At the time of disclosure:
- No active exploitation confirmed
- No public exploit code available
However, due to the critical severity and MSP exposure, delayed patching increases risk over time.
Final Takeaway
CVE-2025-14265 represents a serious integrity and supply-chain risk for ScreenConnect servers. While exploitation requires elevated access, the potential impact is severe once that access is obtained.
Organizations running on-premises ScreenConnect should upgrade to version 25.8 immediately, audit installed extensions, and tighten administrative controls to reduce future risk.
