CriticalCVE-2021-22681

    Rockwell Multiple Products Insufficient Protected Credentials Vulnerability (CVE-2021-22681)

    Published In CISA KEV since Sources: CVE.org

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    What is affected, what to do

    Rockwell Automation Studio 5000 Logix Designer Versions 21 and later, and RSLogix 5000 Versions 16 through 20 use a key to verify Logix controllers are communicating with Rockwell Automation CompactLogix 1768, 1769, 5370, 5380, 5480: ControlLogix 5550, 5560, 5570, 5580; DriveLogix 5560, 5730, 1794-L34; Compact GuardLogix 5370, 5380; GuardLogix 5570, 5580; SoftLogix 5800. Rockwell Automation Studio 5000 Logix Designer Versions 21 and later and RSLogix 5000: Versions 16 through 20 are vulnerable because an unauthenticated attacker could bypass this verification mechanism and authenticate with Rockwell Automation CompactLogix 1768, 1769, 5370, 5380, 5480: ControlLogix 5550, 5560, 5570, 5580; DriveLogix 5560, 5730, 1794-L34; Compact GuardLogix 5370, 5380; GuardLogix 5570, 5580; SoftLogix 5800.

    The vulnerability is being actively exploited; treat it as a priority. The available sources name no fixed version. Check the vendor guidance in the references below. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Rockwell Automation Studio 5000 Logix Designer, RSLogix 5000, Logix Controllers eq RSLogix 5000 Versions 16 through 20..RSLogix 5000 Versions 16 through 20
    • Rockwell Automation Studio 5000 Logix Designer, RSLogix 5000, Logix Controllers eq Studio 5000 Logix Designer: Versions 21 and later..Studio 5000 Logix Designer: Versions 21 and later
    • Rockwell Automation Studio 5000 Logix Designer, RSLogix 5000, Logix Controllers eq CompactLogix 1768, 1769, 5370, 5380, 5480..CompactLogix 1768, 1769, 5370, 5380, 5480
    • Rockwell Automation Studio 5000 Logix Designer, RSLogix 5000, Logix Controllers eq ControlLogix 5550, 5560, 5570, 5580..ControlLogix 5550, 5560, 5570, 5580
    • Rockwell Automation Studio 5000 Logix Designer, RSLogix 5000, Logix Controllers eq DriveLogix 5560, 5730, 1794-L34..DriveLogix 5560, 5730, 1794-L34
    • Rockwell Automation Studio 5000 Logix Designer, RSLogix 5000, Logix Controllers eq Compact GuardLogix 5370, 5380..Compact GuardLogix 5370, 5380
    • Rockwell Automation Studio 5000 Logix Designer, RSLogix 5000, Logix Controllers eq GuardLogix 5570, 5580..GuardLogix 5570, 5580
    • Rockwell Automation Studio 5000 Logix Designer, RSLogix 5000, Logix Controllers eq SoftLogix 5800..SoftLogix 5800

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

    Metrics

    9.8

    XIEM Effective CVSS

    Highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: CVE.org

    63.6 %

    EPSS score

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

    Source: FIRST EPSS, percentile 99.23

    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
    227.77 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 exploited
    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
    9.8 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
    9.8
    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
    63.6 %
    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
    99.23
    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
    CISA assessment (SSVC)
    Exploitation: active · automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 5 March 2026
    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-522

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw lets an attacker with network access — no credentials, no user interaction — impersonate legitimate engineering software towards Logix controllers, with full confidentiality, integrity and availability impact up to and including logic changes on safety-rated GuardLogix systems. Exploitation likelihood is rated very high, and typical targets are manufacturing, energy, water and process industries — squarely the KRITIS population. CISA does not flag known ransomware use; the risk here is primarily manipulation of physical processes rather than encryption. Controllers reachable from IT networks or remote-access paths are top priority; tightly isolated cells with key switches locked in RUN can follow, but must be committed to a CIP Security roadmap.

    1. Runbook step 1

      Immediate response (0-24 h)

      • No conventional patch: The flaw is a discoverable verification key in the protocol between Studio 5000 Logix Designer / RSLogix 5000 and Logix controllers. Rockwell provides hardening guidance and CIP Security-capable firmware rather than a fix — look up the specific firmware levels in the vendor advisory. Treat every network-reachable controller as accessible without authentication.
      • Build the asset inventory now: Identify all CompactLogix 1768/1769/5370/5380/5480, ControlLogix 5550/5560/5570/5580, DriveLogix 5560/5730/1794-L34, Compact GuardLogix 5370/5380, GuardLogix 5570/5580 and SoftLogix 5800 units with IPs and zones. Prioritise anything reachable from the IT network, remote-access VPN or the internet.
      • Cut external exposure: Block EtherNet/IP (44818/TCP, 44818/UDP) and implicit I/O (2222/UDP) at every perimeter and IT/OT boundary. Verify via Shodan/Censys or an external scan whether any controller is internet-facing; if so, isolate immediately.
      • Mode switch to RUN: On controllers with a physical key switch, set it to RUN and remove the key — this blocks program downloads and online edits even if authentication is bypassed. Move to REM/PROG only in documented maintenance windows.
      • Secure a program baseline: Upload current controller projects and compare against the approved release (FactoryTalk AssetCentre or the Logix Designer Compare Tool) to rule out prior tampering.
      • Review remote access: Suspend active integrator/vendor remote sessions pending review and rotate credentials for engineering workstations.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation (IEC 62443 zones/conduits): Place controllers in dedicated cell zones; permit CIP on 44818/TCP only from named engineering workstations and HMI/SCADA servers (allowlist by IP, ideally MAC). Drop and log everything else.
      • CIP Security / Trusted Slot: Where hardware supports it (e.g. the 5580 family with CIP Security-capable comms modules), enable CIP Security so only authenticated endpoints can connect. On ControlLogix, use the Trusted Slot feature to restrict communication to defined chassis slots. Check minimum firmware in the vendor advisory.
      • Industrial firewall / DPI: Deploy a CIP-aware firewall in front of controllers; restrict write services (program download, mode change, tag writes) to engineering hosts and limit HMIs to read-only.
      • Engineering workstation hardening: Run Studio 5000 Logix Designer only on dedicated, hardened hosts without internet or email; enforce application allowlisting (AppLocker/WDAC) and MFA for logon and jump-host access.
      • Remote access: Vendor access only via an MFA-protected jump host with session recording and time-boxed enablement; no direct VPN path into the cell zone.
      • Controller-side hardening: Disable unused comms modules/ports; use source/execution protection and FactoryTalk Security for project files (does not stop the bypass, but raises the bar for follow-on actions).

    3. Runbook step 3

      Detection rules

      • Zeek/Suricata (ENIP/CIP): Alert on CIP sessions (Register Session, Forward Open) to controller IPs from sources outside the engineering allowlist. With the ICSNPP ENIP/CIP parser: filter enip.log/cip.log on id.resp_p == 44818 and id.orig_h not in engineering_hosts.
      • Critical CIP services: Treat program download, online edits, run/program mode changes and firmware updates outside approved windows as high severity; correlate source with change tickets.
      • Controller events / change detection: Review the Controller Log (5580) or FactoryTalk AssetCentre for unexpected project changes, major/minor faults, mode changes and new connections; escalate any deviation from baseline.
      • Flow anomalies: New communication pairs towards controllers (Zeek conn.log, NetFlow) — Sigma shape: dst_port: 44818 AND NOT src_ip|cidr: <engineering_subnet>. Also flag 44818/UDP List Identity sweeps originating from IT networks.
      • Engineering hosts (Sysmon): EID 1 for Logix Designer/RSLinx processes on non-approved systems; EID 3 to destination port 44818 from non-Rockwell processes (e.g. Python, PowerShell).

    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

    Rockwell Automation Studio 5000 Logix Designer Versions 21 and later, and RSLogix 5000 Versions 16 through 20 use a key to verify Logix controllers are communicating with Rockwell Automation CompactLogix 1768, 1769, 5370, 5380, 5480: ControlLogix 5550, 5560, 5570, 5580; DriveLogix 5560, 5730, 1794-L34; Compact GuardLogix 5370, 5380; GuardLogix 5570, 5580; SoftLogix 5800. Rockwell Automation Studio 5000 Logix Designer Versions 21 and later and RSLogix 5000: Versions 16 through 20 are vulnerable because an unauthenticated attacker could bypass this verification mechanism and authenticate with Rockwell Automation CompactLogix 1768, 1769, 5370, 5380, 5480: ControlLogix 5550, 5560, 5570, 5580; DriveLogix 5560, 5730, 1794-L34; Compact GuardLogix 5370, 5380; GuardLogix 5570, 5580; SoftLogix 5800.

    Source: cvelistv5, NVD (NIST), 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
    —Rockwell Automation Studio 5000 Logix Designer, RSLogix 5000, Logix Controllers
    • ControlLogix 5550, 5560, 5570, 5580
    • DriveLogix 5560, 5730, 1794-L34
    • SoftLogix 5800
    • Compact GuardLogix 5370, 5380
    • Studio 5000 Logix Designer: Versions 21 and later
    • RSLogix 5000 Versions 16 through 20
    • GuardLogix 5570, 5580
    • CompactLogix 1768, 1769, 5370, 5380, 5480
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    • —
    rockwellautomationfactorytalk_services_platform
    • ≥ 2.10
    • —
    rockwellautomationrslogix_5000
    • 16 – ≤ 20
    • —
    rockwellautomationstudio_5000_logix_designer
    • ≥ 21.0
    • —

    Vendors and products

    Weakness classes (CWE)

    • CWE-522Insufficiently Protected Credentials

      Class

      The product transmits or stores authentication credentials, but it uses an insecure method that is susceptible to unauthorized interception and/or retrieval.

      Entry at MITRE CWE-522

    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
    PoC-in-GitHub (nomi-sec)cip-security-poc (opens in a new tab)github.comPoC (publicly reported)reported, not verified

    References & sources

    • us-cert.cisa.govics/advisories/icsa-21-056-03x_refsource_MISC, Third-party advisory, US government resource
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2021-22681government-resource, US government resource
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    <a href="https://intel.neosec.eu/en/cve/CVE-2021-22681"><img src="https://intel.neosec.eu/badge/cve/CVE-2021-22681.svg?lang=en" alt="CVE-2021-22681 – NEOSEC Intel" height="20"></a>