ConnectWise ScreenConnect: privilege escalation flaw under attack

What is affected

ConnectWise ScreenConnect is mostly run by companies, schools and public bodies, not on home computers. You are unlikely to have it yourself, but organisations that hold your data may. Breaches that start with flaws like this one are how personal data ends up leaked.

ConnectWise ScreenConnect contains both an improper privilege management and missing authorization vulnerability that may allow an attacker to transfer and execute files through an active remote session without authorization or host confirmation.

What an attacker can do

This is a privilege escalation flaw. It lets an attacker turn limited access into full administrator control. Attackers pair it with another flaw or a malicious file: once anything of theirs runs on the device, this bug lets it take over completely.

How it is reached

Over the internet or network

Access the attacker needs

A basic user account

Does the victim have to do something?

No, works without the victim doing anything

What to do

1. At home: nothing to install. Keep your own devices updated and use a different password for every service, so that a breach at one organisation does not open your other accounts.
2. If you administer ConnectWise ScreenConnect at work: apply the vendor's fix or mitigation now and review logs for signs of compromise, because the flaw was being exploited before it was listed.
3. If the product is past its support date and no fix exists, take it off the internet or retire it.

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

Vendor advisories and fixes

• connectwise.comwww.connectwise.com/company/trust/security-bulletins/2026-09-08-screenconnect-bulletin

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on September 11, 2026, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by September 14, 2026, a deadline that has already passed. That deadline does not bind anyone else, but it shows how seriously the agency rates it.

The EPSS model estimates a 0.9% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 59% of all scored vulnerabilities.

Its CVSS severity score is 9.9 out of 10 (critical), as recorded in the US National Vulnerability Database.

Technical description

A condition in the ScreenConnect client may allow files to be transferred and executed through an active remote session without authorization or Host confirmation in certain circumstances. ScreenConnect servers are not impacted.