ConnectWise ScreenConnect (ConnectWise Control), a widely used remote-access and remote-monitoring tool, contains an authentication bypass (CWE-288) in its management interface. An attacker needs only network access to the management interface to trigger the flaw, with no valid credentials or user interaction required. A successful attacker gains administrative control of the ScreenConnect server by creating a new administrator-level account, providing a foothold that has already been used in ransomware campaigns against downstream managed environments. Any organization running ConnectWise ScreenConnect is affected, especially managed service providers and IT teams whose management interface is reachable from the internet; the source data specifies affected products but no version ranges. Exploitation is confirmed and urgent: CISA added the flaw to the KEV on 2024-02-22 with known ransomware use, EPSS assigns a 100% probability of exploitation within 30 days, and ConnectWise warned that no patch was available at the time of disclosure.
What to do: Follow ConnectWise's instructions immediately: no patch existed at disclosure, so apply the vendor's mitigations or, per the CISA KEV required action, restrict internet exposure of the management interface or discontinue use until mitigations are available, then upgrade to the vendor's patched release as soon as it ships. Audit ScreenConnect servers for unexpectedly created administrator-level accounts and unusual remote sessions, which are the attack's artifacts. Prioritize any instance whose management interface is reachable from the internet, given confirmed in-the-wild exploitation and known ransomware use.
Affected
ConnectWise ScreenConnect
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Estimated exposure
masstens of thousands of internet-exposed ScreenConnect servers (on the order of 10,000-30,000 instances in public internet scans at disclosure), managing millions… — ScreenConnect is a mass-market remote access/RMM product used by thousands of MSPs and IT departments, and public internet scans around disclosure showed tens of thousands of exposed instances whose managed client fleets reach millions of…
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
Description
ConnectWise ScreenConnect 23.9.7 and prior are affected by an Authentication Bypass Using an Alternate Path or Channel vulnerability, which may allow an attacker direct access to confidential information or critical systems.
CISA Known Exploited Vulnerability
Affected
ConnectWise ScreenConnect
Required action
Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
Microsoft reports China-linked ransomware group Storm-1175 switched from Medusa to a new C++ strain, StormEncryptor, likely exploiting N-able flaw CVE-2026-18577.
Microsoft Threat Intelligence reports that the financially motivated, China-linked group Storm-1175 began deploying a new ransomware strain called StormEncryptor on August 2, 2026, replacing its previous Medusa ransomware. StormEncryptor is written in C++, appends the .encrypted extension to files, and drops a !!!README_FIRST!!!.txt ransom note in each scanned directory. Microsoft assesses the group is likely exploiting CVE-2026-18577, an authentication bypass in N-able disclosed on August 2, 2026 and added to CISA's Known Exploited Vulnerabilities catalog the next day. Since 2023, Storm-1175 has exploited more than 16 vulnerabilities in products including Microsoft Exchange, Ivanti, ConnectWise ScreenConnect, JetBrains TeamCity, SimpleHelp, CrushFTP, and GoAnywhere MFT, often moving from initial access to data theft and ransomware deployment within days.
ConnectWise warns of an unpatched ScreenConnect flaw affecting file transfer in support sessions and shares interim mitigations for MSPs.
ConnectWise disclosed a new ScreenConnect Remote Access vulnerability affecting file transfer behavior in both cloud and on-premises deployments; no CVE ID or patch is available yet, with a fix planned later this week. The vendor published temporary mitigation steps that remove TransferFiles permissions from session groups across all roles. Shadowserver tracks nearly 6,000 internet-exposed ScreenConnect instances. Previous ScreenConnect flaws, including CVE-2024-1709, were exploited by ransomware gangs and North Korea's Kimsuky, and three ScreenConnect vulnerabilities are on CISA's actively exploited catalog.