Rockwell Automation Studio 5000 & RSLogix 5000 Hardcoded Cryptographic Key Vulnerability (CVE-2021-22681) Technical Advisory
Executive & SecOps Summary
SECOPS ASSESSMENTRockwell Automation Studio 5000 Logix Designer v21 and later, RSLogix 5000 v16 through v20, and associated Logix controllers
Unauthenticated remote attackers can obtain the hardcoded cryptographic key, bypass verification mechanisms, and gain unauthorized access to modify controller logic or configurations
Implement network segmentation, restrict EtherNet/IP ports, transition controller keyswitches to 'Run' mode, and deploy CIP Security where applicable
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
To mitigate this vulnerability, administrators should upgrade to software and firmware versions that support CIP Security to enforce robust cryptographic authentication. Use the following PowerShell command to audit installed versions of Studio 5000 and RSLogix 5000 on engineering workstations:
# PowerShell script to audit installed Rockwell software versions
Get-WmiObject -Class Win32_Product | Where-Object { $_.Name -like '*Studio 5000*' -or $_.Name -like '*RSLogix 5000*' } | Select-Object Name, Version2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, restrict network access to EtherNet/IP ports (TCP/UDP 44818 and UDP 2222) and switch the physical controller keyswitch to 'Run' mode to prevent unauthorized online programming. Below is an iptables configuration to restrict access on an industrial gateway:
# Allow EtherNet/IP traffic only from a trusted engineering workstation (e.g., 192.168.1.50)
iptables -A INPUT -p tcp -s 192.168.1.50 --dport 44818 -j ACCEPT
iptables -A INPUT -p udp -s 192.168.1.50 --dport 44818 -j ACCEPT
iptables -A INPUT -p udp -s 192.168.1.50 --dport 2222 -j ACCEPT
iptables -A INPUT -p tcp --dport 44818 -j DROP
iptables -A INPUT -p udp --dport 44818 -j DROP
iptables -A INPUT -p udp --dport 2222 -j DROP3. Log Audit & IoC Verification Commands
Monitor network traffic for unauthorized connection attempts to the controllers. The following tshark command can be used to analyze packet captures for unexpected IP addresses communicating over EtherNet/IP ports:
# Analyze PCAP file to identify all source IPs communicating over TCP port 44818
tshark -r network_traffic.pcap -Y 'tcp.port == 44818' -T fields -e ip.src -e ip.dst -e tcp.flags.str | sort | uniq -cBlock Exploits Instantly with Managed Virtual Patching Rules
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Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2021-22681) exists in Rockwell Automation Studio 5000 Logix Designer and RSLogix 5000 due to the use of a hardcoded cryptographic key to verify communications with Logix controllers. Because the secret key is statically embedded within the software binaries (CWE-522), it can be extracted through reverse engineering or static analysis.
2. Exploitation Mechanics & Attack Scenario
An attacker who successfully extracts the hardcoded key can craft malicious authentication payloads that mimic legitimate Studio 5000 or RSLogix 5000 engineering workstations. Since the target Logix controllers rely on this hardcoded key to verify the authenticity of the connecting client, they will accept the unauthorized connection as trusted. This allows the attacker to bypass authentication entirely, upload malicious logic, modify configurations, or issue control commands directly to the PLC.
3. Infrastructure & Business Impact
With a CVSS score of 9.8 (Critical) and its inclusion in the CISA KEV catalog, this vulnerability poses an active and severe threat to industrial control systems (ICS). Successful exploitation in operational technology (OT) environments can lead to unauthorized process modifications, equipment damage, unplanned downtime, and potential safety hazards, severely impacting business continuity and physical safety.
Official Vendor Advisories & References
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.
Frequently Asked SecOps Questions (CVE-2021-22681)
FAQQ1. How critical is CVE-2021-22681 and is it actively exploited in the wild?
CVE-2021-22681 is rated CVSS 9.8 (CRITICAL) with a 30-day EPSS exploitation probability of 63.6%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2021-22681?
Primary impacted vendors include rockwell automation across studio 5000 logix designer, rslogix 5000, compactlogix, controllogix, drivelogix, compact guardlogix, guardlogix, softlogix. Scope summary: Studio 5000 Logix Designer Versions 21 and later, RSLogix 5000 Versions 16 through 20 Affected Controllers: 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
Q3. What temporary mitigations or workarounds exist for CVE-2021-22681 before patching?
[Mitigation] Implement network segmentation, restrict EtherNet/IP ports, transition controller keyswitches to 'Run' mode, and deploy CIP Security where applicable Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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