CriticalCVE-2024-1709

    Authentication bypass using an alternate path or channel (CVE-2024-1709)

    Published In CISA KEV since Sources: NCSC NZ, pwn.watch, CVE.org

    What is affected, what to do

    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.

    The vulnerability is being actively exploited; treat it as a priority. CISA lists it as used in ransomware campaigns. Update screenconnect to version 23.9.8. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • ConnectWise ScreenConnect lte *..23.9.7

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    10.0

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    10.0

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: NCSC NZ, pwn.watch, CVE.org

    99.98 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 99.98

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    259.53 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploitedSource: NCSC NZ How we classify
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    10.0 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    10.0
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    99.98 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    99.98
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-288

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This is a trivially exploitable flaw: network-reachable without authentication, where one crafted request yields admin rights on a tool built to remotely control every managed endpoint. Public exploits appeared almost immediately after disclosure, and the exploitation likelihood is among the highest of any CVE. CISA explicitly flags it as used in ransomware campaigns. Typical targets are MSPs and organisations self-hosting remote-support access, where a single compromised server gives attackers a path into many downstream customers (supply-chain risk). Treat any internet-facing unpatched instance as a top-priority emergency and as compromised until proven otherwise.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Upgrade all on-prem instances to ScreenConnect 23.9.8 or later now. Every version up to and including 23.9.7 is affected. Cloud instances (screenconnect.com, hostedrmm.com) are patched by the vendor, but still verify the version shown in the admin UI.
      • If you cannot upgrade immediately, take the server off the internet. Block the web port (default TCP 8040) and the relay port (default TCP 8041) at the perimeter until the patch is in.
      • Check for compromise before reconnecting. Review App_Data\User.xml for unknown administrator accounts and check its modification timestamp. Also look for unexpected .aspx or .ashx files under App_Extensions\. Exploitation is routinely chained with CVE-2024-1708 (extension path traversal) to reach remote code execution.
      • If you find any indicator, treat the host as fully compromised. Image it for forensics, then rebuild. After that, reset every ScreenConnect account and every credential used through or stored in ScreenConnect, including domain admin and service accounts.
      • Treat managed endpoints as downstream targets. An attacker with admin access can push commands to every connected client. Run an EDR hunt from 19 Feb 2024 onwards across all hosts with the ScreenConnect client.
      • If an MSP runs ScreenConnect for you, demand written confirmation of patch level and compromise assessment. Evaluate your NIS2 early-warning obligation (24 h).

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Expose the web UI only via VPN or ZTNA. Otherwise, restrict access to an allowlist of fixed technician source IPs.
      • WAF/reverse proxy: Deny any request to /SetupWizard.aspx, particularly with a trailing path segment (regex (?i)/SetupWizard\.aspx/.+). No legitimate user needs this path once initial setup is complete.
      • IPS: Enable the Suricata/ET Open or Snort signatures for CVE-2024-1709 (search for "ScreenConnect SetupWizard") and run them in blocking mode.
      • Endpoint hardening: Use EDR or ASR rules to block ScreenConnect.Service.exe and its web host from spawning cmd.exe, powershell.exe, rundll32.exe or certutil.exe.
      • IAM: Keep local ScreenConnect accounts to a minimum and enforce MFA or SSO. Never run the service under a domain admin context.
      • File integrity: Put FIM on App_Data\User.xml, App_Data\*.xml and App_Extensions\, and alert on any change.

    3. Runbook step 3

      Detection rules

      • Web/proxy logs: Requests to SetupWizard.aspx with an extra path segment indicate exploitation, especially POST requests from external IPs. SPL: index=proxy uri_path="*SetupWizard.aspx/*" | stats count by src_ip, http_method
      • Sysmon EID 11 / FIM: Writes to \ScreenConnect\App_Data\User.xml, or new files under \App_Extensions\. KQL: DeviceFileEvents | where FolderPath has @"ScreenConnect\App_Extensions" and (FileName endswith ".ashx" or FileName endswith ".aspx")
      • Process ancestry (EDR, Sysmon EID 1): ScreenConnect.ClientService.exe or ScreenConnect.Service.exe spawning cmd.exe or powershell.exe with -enc, DownloadString, Invoke-WebRequest or certutil -urlcache. Sigma shape: ParentImage|endswith: ScreenConnect.*.exe AND Image|endswith: [cmd.exe, powershell.exe].
      • Windows Security 4720/4732 on clients: New local accounts or admin-group additions shortly after a ScreenConnect session. Also watch for new services (7045) and scheduled tasks (4698).
      • Network (Zeek): Unexpected outbound traffic from the ScreenConnect server, such as tunnelling tools, C2 beacons or downloads from paste and file-hosting sites. Also watch for fan-out of the same payload to many clients within minutes.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    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.

    Source: NCSC NZ (CC BY 4.0), pwn.watch, NVD (NIST), cvelistv5, CISA KEV Catalog, CVE.org (MITRE)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    ConnectWiseScreenConnect
    • ≤ 23.9.7
    • —
    connectwisescreenconnect
    • < 23.9.8
    • 23.9.8

    Vendors and products

    Weakness classes (CWE)

    • CWE-288Authentication Bypass Using an Alternate Path or Channel

      Base

      The product requires authentication, but the product has an alternate path or channel that does not require authentication.

      Entry at MITRE CWE-288

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited
    NCSC NZUnauthenticated Remote Code Execution in ConnectWise's ScreenConnect (opens in a new tab)NCSC NZactively exploited
    Reference tagged as exploitgithub.com (opens in a new tab)PoC (publicly reported)reported, not verified—
    Metasploit Framework (Pull Request)Metasploit PR #18870 (opens in a new tab)github.comPoC (publicly reported)reported, not verified—

    References & sources

    • connectwise.comConnectWise ScreenConnect 23.9.8 security bulletinVendor advisory, pwn-watch
    • huntress.comblog/vulnerability-reproduced-immediately-patch-screenconnect-2…Third-party advisory
    • huntress.comblog/detection-guidance-for-connectwise-cwe-288-2Exploit, Third-party advisory
    • bleepingcomputer.comnews/security/connectwise-urges-screenconnect-admins-to-patch-c…Press coverage, Third-party advisory
    • github.comwatchtowrlabs/connectwise-screenconnect_auth-bypass-add-user-pocExploit, Third-party advisory
    • github.comrapid7/metasploit-framework/pull/18870Issue tracking, Patch, Third-party advisory
    • horizon3.aiattack-research/red-team/connectwise-screenconnect-auth-bypass-…Third-party advisory
    • techcrunch.com2024/02/21/researchers-warn-high-risk-connectwise-flaw-under-at…Press coverage, Third-party advisory
    • securityweek.comconnectwise-confirms-screenconnect-flaw-under-active-exploitati…Press coverage, Third-party advisory
    • huntress.comblog/a-catastrophe-for-control-understanding-the-screenconnect-…Exploit, Third-party advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2024-1709government-resource, US government resource
    • pwn.watchpwn.watch: ConnectWise ScreenConnect auth bypass mass-exploitedpwn-watch
    • NVD (NIST)NVD: CVE-2024-1709pwn-watch
    • NVD (NIST)NVD: CVE-2024-1708pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch
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