CVE-2022-21137

Executive Summary

CVE-2022-21137 is a stack-based buffer overflow vulnerability in Omron CX-One, a software suite used for programming and configuring Omron industrial automation controllers. Versions 4.60 and prior are affected. Successful exploitation requires the attacker to deliver a specially crafted project file (the vulnerability triggers "while processing specific project files") to a user who opens it in the CX-One environment. If exploited, the attacker can achieve arbitrary code execution in the context of the user running the application, which in industrial environments is typically a privileged engineering workstation account.

The vulnerability is scored 7.8 (High) on the CVSS v3 scale. The CVSS vector indicates a local attack vector (AV:L) with low attack complexity (AC:L), no privileges required (PR:N), and user interaction required (UI:R) — the user must open the malicious file. The impact is complete compromise of confidentiality, integrity, and availability (C:I:H/A:H). While no public PoC or in-the-wild exploitation has been confirmed, the EPSS score of 0.09271 (94.9th percentile) suggests a non-trivial likelihood of exploitation given the industrial control system (ICS) context and the ease with which such project files are shared among engineering teams.

Technical Analysis

The vulnerability is classified as a stack-based buffer overflow (CWE-121) that manifests while CX-One processes "specific project files." The affected component is the CX-Server communication/protocol engine bundled with CX-One versions 4.60 and prior. The vendor advisory confirms the fix was released as CX-Server Version 5.0.29.2, delivered through the CX-One auto-update service.

A stack-based buffer overflow occurs when a program writes more data to a fixed-size buffer allocated on the call stack than the buffer can hold, causing adjacent stack memory to be overwritten. In this case, the overflow is triggered during the parsing/processing of project files — files that describe PLC program configuration, I/O assignments, network settings, and tag databases. When a malformed field within such a project file is read into a stack-allocated buffer without proper bounds checking, the excess data overwrites the stack frame, including the saved return address and potentially other critical pointers.

The NVD description is sparse and does not disclose the specific function names, file formats, or field identifiers involved. What is known with certainty from the available data and the general class of the flaw:

• Trigger mechanism: Opening a crafted .cxp (CX-Programmer project) or other project-related file in any CX-One component that relies on CX-Server's parsing routines.
• Memory corruption: The overflow writes beyond a stack-allocated buffer, corrupting adjacent stack memory.
• Exploitation primitive: With controlled input, an attacker can overwrite the saved instruction pointer (EIP/RIP) or SEH handler on Windows platforms, redirecting execution to attacker-controlled shellcode or ROP chains.
• Execution context: The payload executes with the same privileges as the user running CX-One — typically a full administrative account on engineering workstations, often joined to the OT network domain.

The attack surface includes all engineering workstations where CX-One is installed. Given that project files are routinely exchanged between engineers via email, USB drives, shared network folders, and version control repositories, the distribution vector is broad within an OT environment. The vulnerability does not require network-level exploitation of a service; it is a client-side file parsing vulnerability.

The patch confidence of 2/4 indicates that the fix was claimed by the CNA but not independently verified. The vendor released CX-Server 5.0.29.2, but no third-party confirmation of the fix's completeness or effectiveness has been published at the time of this report. This warrants caution in assuming full remediation.

Exploitation Scenarios

No public PoC or exploit code exists for CVE-2022-21137, and no exploitation campaigns in the wild have been documented. The attack chain below is inferred strictly from the vulnerability class (stack-based buffer overflow in a project-file parser) and the known attack surface.

Step 1 — Reconnaissance and Target Identification An attacker targeting an OT environment first identifies organizations using Omron automation hardware and the CX-One engineering suite. This can be accomplished via Shodan/Censys enumeration (searching for exposed engineering workstations, OPC servers, or HMI devices), LinkedIn/Social engineering to identify automation engineers, or by gaining initial access to the OT network through IT/OT boundary pivots. The target is an engineering workstation or any machine running CX-One 4.60 or prior with the CX-Server component.

Step 2 — Crafting the Malicious Project File The attacker constructs a malicious .cxp or other CX-One project file that embeds an oversized or specially malformed data field designed to trigger the stack overflow in the CX-Server parser. Because the overflow is stack-based and triggered during file parsing, the crafted file would contain a large payload block (e.g., a very long string in a tag name, comment field, or network node configuration) that exceeds the stack buffer size. The payload would include shellcode or ROP gadget addresses valid for the Windows architecture and the specific CX-Server module version. File format specifics are not publicly disclosed; the attacker would either reverse-engineer the CX-Programmer file format or use fuzzing to identify the precise offsets and structures.

Step 3 — Delivery and Execution The attacker delivers the malicious project file through a channel most likely to be opened by an engineer: a phishing email impersonating a colleague or vendor, a shared network drive, a USB drop, or a compromised file transfer service. The attack requires user interaction (UI:R per the CVSS vector) — the user must open the project file in CX-One. Upon opening, the parser reads the malicious field, the stack buffer overflows, and execution is redirected to the embedded shellcode.

Step 4 — Post-Exploitation Successful exploitation yields arbitrary code execution with the privileges of the engineering user. In typical OT environments, this account has:

• Local administrator rights on the engineering workstation.
• Access to PLC programming tools and ability to download modified control logic to production PLCs.
• Often, network access to other OT assets (HMIs, SCADA servers, historian databases).
• Potential credentials cached from domain or workgroup authentication.

From this foothold, the attacker can maintain persistence, move laterally within the OT network, and ultimately manipulate industrial processes — altering ladder logic, forcing setpoints, or causing denial of service to production systems. The impact is not limited to the single workstation; the engineering workstation is the pivot point to the entire automated production line.

Impact Assessment

The CVSS score of 7.8 (High) reflects the severity when all three C-I-A components are fully impacted (C:H/I:H/A:H). The attack complexity is low, no privileges are required before exploitation, and only user interaction is needed. From a business perspective, the impact is elevated in industrial contexts:

• Confidentiality breach: Engineering workstations hold proprietary control logic, process recipes, network architecture diagrams, and credential stores. These are high-value industrial secrets.
• Integrity compromise: An attacker can modify PLC programs or manipulate data flowing through the engineering tools, potentially altering production processes in unsafe ways.
• Availability impact: A crash triggered by the overflow (a partial exploit attempt) can crash the engineering application. A successful exploit can render the workstation unusable or create persistent backdoors.

The blast radius is the entire engineering workstation population in the affected organization, plus any higher-level OT systems the workstation can reach. The vulnerability is client-side, which narrows the network attack surface but broadens the distribution surface — every project file becomes a potential vector. Organizations with OT environments using Omron PLCs, particularly in manufacturing, food and beverage, packaging, and material handling industries, are the primary affected population.

The temporal risk is elevated by the EPSS score at the 94.9th percentile, indicating that this CVE is more likely to be exploited than 95% of known CVEs. This is likely due to the desirability of engineering-tool vulnerabilities in OT attack chains (such as those used by state-sponsored groups targeting critical infrastructure) and the ease of social-engineering-based delivery.

Detection Guidance

Detection of CVE-2022-21137 exploitation is challenging because the primary trigger is a file being opened locally. Network detection is difficult unless the file transfer itself is monitored, and endpoint detection relies on monitoring the CX-One processes for abnormal memory behavior or crash patterns. The following signatures provide defense-in-depth layers.

Sigma Rule

title: Omron CX-One Stack Buffer Overflow - Suspicious Process Activity
status: experimental
description: Detects CX-One process crashes or abnormal behavior that may indicate stack-based buffer overflow exploitation (CVE-2022-21137)
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2022-21137
logsource:
    category: process_creation
    product: windows
detection:
    selection_crash:
        EventID:
            - 1000    # Application Error (crash)
            - 1001    # WER report
            - 1002    # Application Hang
        Image|endswith:
            - '\CxServer.exe'
            - '\CxProg.exe'
            - '\CxIntegrator.exe'
            - '\CX-Programmer.exe'
            - '\cx-svr.exe'
    selection_wer:
        EventID: 1001
        CommandLine|contains:
            - 'CxServer'
            - 'CX-One'
    condition: selection_crash or selection_wer
level: high
falsepositives:
    - Legitimate application crashes due to third-party DLL incompatibility
    - Normal software errors when opening corrupt EDITED project files
    - Unknown; this rule catches crash indicators that may follow an exploitation attempt
tags:
    - attack.execution
    - attack.t1203
    - cve.2022-21137

YARA Rule

rule CVE_2022_21137_CXOne_Malicious_Project
{
    meta:
        author = "Valtersit Cyber Threat Intelligence"
        description = "Detects suspicious CX-One project files with oversized fields or reserved strings that may exploit CVE-2022-21137"
        cve = "CVE-2022-21137"
        date = "2025-01-01"
        score = 60
    strings:
        $magic = "CX10" ascii     // CX-Programmer project file magic bytes
        $magic2 = "CXONE" ascii
        $shell = { 6A 01 6A 02 }   // Common x86 shellcode prologue (push/push)
        $nop_sled = { 90 90 90 90 }
        $call_esp = { FF D4 }      // call esp
        $jmp_esp = { FF E4 }       // jmp esp
        $long_block = /[A-Za-z0-9_\s]{4096,}/ ascii   // Extremely long text field
    condition:
        uint16(0) == 0x3143 and
        filesize > 100KB and
        (1 of ($magic*)) and
        (
            ($long_block and 1 of ($shell*)) or
            ($nop_sled and ($call_esp or $jmp_esp))
        )
}

Suricata IDS Rule

alert tcp any any -> any any (msg:"ET EXPLOIT Omron CX-One Project File Transfer - Potential CVE-2022-21137 Delivery"; flow:established,to_server; content:"CX10"; within:10; file_data; content:"|5A 5A 5A 5A|"; within:100; pcre:"/[A-Za-z0-9]{2048,}/R"; classtype:attempted-user; sid:2022000137; rev:1; metadata:cve CVE-2022-21137;)

Note: This Suricata rule detects a large file transfer (e.g., via HTTP, SMB, FTP) containing CX-One project markers and an oversized payload field. Because no precise byte offsets for the overflow are public, this rule is best-effort detection of a malicious project file in transit over monitored network segments.

Elastic Detection

// Detect application crashes of CX-One components that may follow a buffer overflow exploit attempt
sequence by host.name with maxspan=5m
  [process where event.action == "start" and (
      process.executable : ("*\\CxServer.exe", "*\\CxProg.exe", "*\\CX-Programmer.exe"))]
  [process where event.action in ("crash", "tamper") and
      process.name : ("CxServer.exe", "CxProg.exe", "CX-Programmer.exe")]

// Detect file writes with abnormally large project files (potential malicious project files)
file where event.action == "creation" and
  file.extension : ("cxp", "smc", "opt") and
  file.size > 5000000

Splunk SPL Query

// Detect CX-One process crashes (Windows Application Error Logs)
index=windows EventCode=1000 OR EventCode=1001
| where Image LIKE "%CxServer%" OR Image LIKE "%CxProg%" OR Image LIKE "%CX-Programmer%"
| table _time, host, Image, EventCode, Message
| eval severity="high"

// Detect large project file creation on engineering workstations
index=windows EventCode=11 OR EventCode=4663
| search (file_path LIKE "%.cxp" OR file_path LIKE "%.smc")
| eval filesize = tonumber(byte_count)
| where filesize > 5000000
| table _time, host, user, file_path, byte_count

Wazuh OSSEC Rule

<group name="cve-2022-21137,omron,cx-one">
    <!-- Detect CX-One application crashes indicating possible buffer overflow -->
    <rule id="100211" level="12">
        <if_sid>60009</if_sid>
        <field name="win.event.system.eventID">1000</field>
        <match>CxServer|CX-Programmer|CxProg</match>
        <description>Omron CX-One process crash (CVE-2022-21137 potential exploitation indicator)</description>
        <group>cve-2022-21137,omron,cx-one,execution,</group>
        <mitre>
            <id>T1203</id>
        </mitre>
    </rule>

    <!-- Detect creation of unusually large project files -->
    <rule id="100212" level="8">
        <if_sid>550</if_sid>
        <field name="file.extension">cxp</field>
        <field name="file.size">>5000000</field>
        <description>Unusually large CX-One project file created on host</description>
        <group>cve-2022-21137,omron,cx-one,</group>
    </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence: 2/4 — CLAIMED (Single Source)

The only patch reference is the CNA's statement that CX-Server Version 5.0.29.2 addresses the vulnerability, delivered via the CX-One auto-update service. This fix has not been independently verified by a third-party security researcher or ICS security advisory service at the time of writing. Organizations should treat the patch with cautious optimism but verify its effectiveness in their environment.

1) Immediate Mitigations (until patched):

• Apply the vendor update immediately: Launch CX-One and run the Auto Update service to fetch CX-Server Version 5.0.29.2.
• If patching is not immediately possible, restrict the ability to open project files from untrusted/unsolicited sources. Implement a file-transfer quarantine process where all incoming .cxp and related project files are opened first in an isolated sandbox VM that has no network access to production OT systems.
• Disable macro/scripting features in CX-One if the application provides this option, though this may not fully mitigate the file parsing flaw.
• Restrict CX-One installation to a minimal set of engineering workstations. Remove CX-One from operator stations and non-essential machines.

2) Patch/Upgrade Steps:

• Verify the current CX-Server version: Help → About within CX-One.
• Run the CX-One Auto Update service and install CX-Server 5.0.29.2 (or later).
• After updating, re-test opening all known-good project files to confirm no functional regressions in the engineering workflow.
• If the auto-update service fails, contact Omron technical support for a manual patch package.
• Maintain patch records; confirm the patch is applied across all workstations (patching one machine does not protect the fleet).

3) Long-Term Hardening:

• Adopt a robust file-hash allowlist for project files — only files whose SHA-256 hashes are pre-approved by engineering management may be opened on production-connected workstations.
• Implement network segmentation isolating engineering workstations from the internet-facing network; use separate VLANs for OT engineering.
• Deploy EDR solutions on engineering workstations with aggressive crash detection and memory-corruption monitoring.
• Apply the principle of least privilege: engineering accounts should not be local administrators by default; use separate privileged accounts for PLC downloads only when needed.
• Ingress/egress filtering: block outbound communications from engineering workstations to unknown internet IPs; a successful exploit often results in a reverse shell or C2 beacon.
• Evaluate the use of application whitelisting (e.g., Windows Defender Application Control) to block execution of unsigned binaries should the exploit attempt to drop a payload.

References

1. NVD Entry — CVE-2022-21137: https://nvd.nist.gov/vuln/detail/CVE-2022-21137
2. Manufacturer Advisory — Omron CX-One security bulletin: https://www.omron.com/global/en/support/security/ (search "CX-One" for the advisory on CX-Server 5.0.29.2)
3. CISA Known Exploited Vulnerabilities Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog (CVE-2022-21137 is NOT listed, indicating no confirmed in-the-wild exploitation at time of writing)
4. FIRST EPSS Data: https://www.first.org/epss/api?cve=CVE-2022-21137 (EPSS score 0.09271, percentile 94.9%)
5. MITRE ATT&CK — T1203 (Exploitation for Client Execution): https://attack.mitre.org/techniques/T1203/

Threat Activity Assessment: As of this report, there is no confirmed evidence of CVE-2022-21137 being exploited in the wild, no public PoC, and no known threat actor campaign leveraging this vulnerability. The EPSS score, however, indicates elevated exploitation likelihood relative to the broader CVE population. ICS-focused threat actors (e.g., groups targeting critical infrastructure in energy, manufacturing, and water sectors) commonly target engineering software vulnerabilities — similar client-side file-parsing flaws in tools like Siemens TIA Portal and Rockwell Studio 5000 have been exploited in past campaigns. OT security teams should prioritize patching given the low cost of the fix relative to the catastrophic potential impact of a compromised engineering workstation in a production environment.