CriticalCVE-2026-84869

    ScreenConnect Client: Guest-to-Host File Execution via File-Transfer Actions (CVE-2026-84869)

    Published Last modified In CISA KEV since Sources: BSI, pwn.watch, CVE.org

    What is affected, what to do

    The vulnerability CVE-2026-84869 allows an attacker to transfer and execute files through active remote sessions without authorization or host confirmation due to improper privilege management and missing authorization. This results in remote code execution (RCE) that can be exploited both pre- and post-authentication. The vulnerability is actively exploited in the wild, including in ransomware campaigns since 2026. Affected products are all versions of ConnectWise ScreenConnect prior to 26.6.5.9742. An immediate update to version 26.6.5.9742 is urgently recommended to mitigate the risk.

    The vulnerability is being actively exploited; treat it as a priority. Update screenconnect to version 26.6.5.9742, ScreenConnect to version 26.6.5. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • ConnectWise ScreenConnect eq All versions prior to 26.6.5..All versions prior to 26.6.5

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

    Metrics

    9.9

    Priority

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

    Source: Vendor (CNA), CVSS v3

    9.9

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: BSI, pwn.watch, CVE.org

    0.9 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 60.2

    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
    204.89 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: VulnCheck KEV (opens in a new tab) 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
    9.9 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
    9.9
    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
    0.9 %
    Low — model estimates < 1% exploitation likelihood.
    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
    60.2
    High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
    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-862, CWE-269

    Response and mitigation

    Why act now?

    Prioritisation rationale

    The flaw is network-reachable with low attack complexity and needs only a low-privileged account with an active session. It lets an attacker execute arbitrary files on the target endpoint, with full confidentiality, integrity and availability impact that crosses the component's scope boundary. EPSS places it only in a moderate band and CISA lists no known ransomware use. However, the KEV listing confirms real-world abuse, and ScreenConnect is a favourite vehicle for remote-access abuse: supply-chain attacks through MSPs, insider misuse and hijacked technician accounts. Treat it as high urgency, to be resolved within days, if you run ScreenConnect yourself or through an IT provider, and as top priority where MSP access reaches OT or critical-infrastructure networks. If no client is installed, the remaining work drops to hunting for rogue instances.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Inventory every ScreenConnect client: Use EDR or software inventory to find all endpoints running the ScreenConnect Client (<instance-id>) service or the ScreenConnect.ClientService.exe / ScreenConnect.WindowsClient.exe processes. The affected build is 26.6.5.9742. The flaw sits in the client; the vendor states that ScreenConnect servers are not impacted.
      • Update the client: A patch is available from the vendor — look up the fixed version in the ConnectWise advisory. For on-prem instances, upgrade the server first so it pushes the corrected client build to agents. Then verify the rollout by checking the service version on endpoints.
      • Hunt for rogue instances: Isolate any endpoint whose client instance ID or relay host does not belong to your own ScreenConnect deployment, and uninstall the service. Unsanctioned cloud relays under *.screenconnect.com are the typical pattern.
      • Kill active sessions: Terminate all live remote-support sessions. Review the server audit logs for the past few weeks for file transfers and "Run Command" events.
      • Rotate credentials: Reset credentials for every technician and MSP account with session rights, since exploitation requires an authenticated session. Enforce MFA for all accounts on the ScreenConnect instance.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation / egress control: Allow outbound traffic to ScreenConnect relays (on-prem defaults TCP 8041 relay and TCP 8040 web, or 443) only to your sanctioned instance. Block all other *.screenconnect.com destinations at the proxy or firewall.
      • IAM / least privilege: In ScreenConnect roles, restrict "Transfer Files", "Run Commands" and "Run Toolbox Items" to a minimal group. Scope MSP accounts to assigned session groups only. Keep host confirmation enabled, but stop treating it as an effective control while this flaw is unpatched.
      • Endpoint hardening: Use AppLocker or WDAC to block execution of binaries and scripts from C:\Windows\Temp\ScreenConnect\ and %ProgramData%\ScreenConnect Client*\. Allowlist only signed, approved tooling.
      • Reduce footprint: Remove the client from systems that do not need remote support, especially domain controllers and servers in critical-infrastructure zones. Where access is required, enable the service only on a just-in-time basis.
      • Session recording: Turn on server-side video recording and logging for all sessions. Forward the logs to the SIEM in tamper-evident form to meet NIS2 evidence requirements.

    3. Runbook step 3

      Detection rules

      • Process ancestry (Sysmon EID 1 / Security 4688): Alert on children of ScreenConnect.ClientService.exe such as cmd.exe, powershell.exe, rundll32.exe, msiexec.exe or unknown executables. KQL: DeviceProcessEvents | where InitiatingProcessFileName =~ "ScreenConnect.ClientService.exe" | where FileName !in~ ("ScreenConnect.WindowsClient.exe")
      • File creation (Sysmon EID 11): Alert on new .exe, .dll, .ps1, .bat or .cmd files under C:\Windows\Temp\ScreenConnect\*\ created outside documented maintenance windows. Sigma shape: TargetFilename|contains: '\Temp\ScreenConnect\' AND TargetFilename|endswith: ['.exe','.dll','.ps1','.bat','.cmd'].
      • Windows Application log: Flag events from source ScreenConnect Client (*) containing "Transferred files" that cannot be matched to a change or support ticket.
      • Network telemetry (Zeek/Suricata): Watch for TLS SNI or DNS lookups for *.screenconnect.com, or TCP 8041 connections to destinations other than your own instance. Also flag unusual upload volumes inside established relay sessions.
      • Server audit: In the ScreenConnect server audit data, correlate file-transfer and queued-command events that have no preceding host-confirmation event.

    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

    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.

    Source: BSI CSAF, BSI WID Portal, pwn.watch, CISA KEV Catalog, cvelistv5, NVD (NIST)

    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
    • All versions prior to 26.6.5
    • < 26.6.5
    • —
    • 26.6.5
    connectwisescreenconnect
    • < 26.6.5.9742
    • 26.6.5.9742

    Vendors and products

    Weakness classes (CWE)

    • CWE-862Missing Authorization

      Class

      The product does not perform an authorization check when an actor attempts to access a resource or perform an action.

      Entry at MITRE CWE-862

    • CWE-269Improper Privilege Management

      Class

      The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor.

      Entry at MITRE CWE-269

    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

    References & sources

    • connectwise.comConnectWise ScreenConnect — CVE-2026-84869pwn-watch
    • github.comConnectWise-Advisories/Disclosures/tree/main/CVE-2026-84869
    • connectwise.comcompany/trust/advisories
    • huntress.comblog/rogue-screenconnect-installationsThird-party advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2026-84869government-resource
    • pwn.watchpwn.watch: ConnectWise ScreenConnect: ConnectWise ScreenConnect Improper Privilege Management and Missing Authorization Vulnerabilitypwn-watch
    • NVD (NIST)NVD: CVE-2026-84869pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: active, automatable: no

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentchanged
      {"id":"CVE-2026-84869","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-09-11T18:50:39.725092Z"}
      {"id":"CVE-2026-84869","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-09-10T00:00:00+00:00"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    2. NVD analysis modifiedNVD

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Reference typeadded
      —
      CISA-ADP: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-84869 Types: US Government Resource
      Reference typeadded
      —
      CISA-ADP: https://www.huntress.com/blog/rogue-screenconnect-installations Types: Third Party Advisory

      Source identifier: nvd@nist.gov

    3. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: active, automatable: no

      Show 3 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-84869
      Referenceadded
      —
      https://www.huntress.com/blog/rogue-screenconnect-installations
      SSVC assessmentchanged
      {"id":"CVE-2026-84869","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-09-10T00:00:00+00:00"}
      {"id":"CVE-2026-84869","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-09-11T18:50:39.725092Z"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    4. Initial analysis by NVDNVD

      Newly listed as affected:
      Show 4 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Product configurationadded
      —
      OR *cpe:2.3:a:connectwise:screenconnect:*:*:*:*:*:*:*:* versions up to (excluding) 26.6.5.9742
      Reference typeadded
      —
      ConnectWise: https://github.com/ConnectWise-Advisories/Disclosures/tree/main/CVE-2026-84869 Types: Third Party Advisory
      Reference typeadded
      —
      ConnectWise: https://www.connectwise.com/company/trust/advisories Types: Vendor Advisory
      Reference typeadded
      —
      ConnectWise: https://www.connectwise.com/company/trust/security-bulletins/2026-09-08-screenconnect-bulletin Types: Vendor Advisory

      Source identifier: nvd@nist.gov

    5. CISA KEV entry updated9119a7d8…

      4 individual changes: Date Added, Due Date, Required Action, Vulnerability Name

      Show 4 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Date Addedadded
      —
      2026-09-11
      Due Dateadded
      —
      2026-09-11
      Required Actionadded
      —
      2026-09-11
      Vulnerability Nameadded
      —
      2026-09-11

      Source identifier: 9119a7d8-5eab-497f-8521-727c672e3725

    Show 3 older changes

    1. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: no

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentchanged
      {"id":"CVE-2026-84869","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-09-09T20:44:52.904981Z"}
      {"id":"CVE-2026-84869","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-09-10T00:00:00+00:00"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    2. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: no

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentadded
      —
      {"id":"CVE-2026-84869","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-09-09T20:44:52.904981Z"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    3. Received7d616e1a…

      CVSS V3.1: AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

      Weakness type: CWE-269, CWE-862

      Description added or changed

      Show 8 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionadded
      —
      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.
      CVSSadded
      —
      AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
      Weakness type (CWE)added
      —
      CWE-269
      Weakness type (CWE)added
      —
      CWE-862
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/84xxx/CVE-2026-84869.json">CVE-2026-84869</a>
      Referenceadded
      —
      https://github.com/ConnectWise-Advisories/Disclosures/tree/main/CVE-2026-84869
      Referenceadded
      —
      https://www.connectwise.com/company/trust/advisories
      Referenceadded
      —
      https://www.connectwise.com/company/trust/security-bulletins/2026-09-08-screenconnect-bulletin

      Source identifier: 7d616e1a-3288-43b1-a0dd-0a65d3e70a49

    Linked advisories

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