{"id":"CVE-2021-22659","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-22659","generatedAt":"2026-10-27T22:26:08.964Z","title":"Rockwell Automation MicroLogix 1400 Version 21.6 and below may allow a remote unauthenticated attacker to send a specially crafted Modbus packet allowing the attacker to retrieve or modify random values in the register.","description":"Rockwell Automation MicroLogix 1400 Version 21.6 and below may allow a remote unauthenticated attacker to send a specially crafted Modbus packet allowing the attacker to retrieve or modify random values in the register. If successfully exploited, this may lead to a buffer overflow resulting in a denial-of-service condition. The FAULT LED will flash RED and communications may be lost. Recovery from denial-of-service condition requires the fault to be cleared by the user.","published":"2021-03-25T16:15:14.000Z","lastModified":"2026-06-17T03:37:32.000Z","status":"Modified","sourceIdentifier":"ics-cert@hq.dhs.gov","cvss":{"version":"3.1","score":8.6,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H"},"cwe":["CWE-120"],"affected":["rockwellautomation/micrologix 1400 firmware"],"epss":{"score":0.01795,"percentile":0.78282,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (1.80%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://rockwellautomation.custhelp.com/app/answers/answer_view/a_id/1129877/loc/en_US#__highlight","tags":["Permissions Required","Vendor Advisory"],"source":"ics-cert@hq.dhs.gov"},{"url":"https://us-cert.cisa.gov/ics/advisories/icsa-21-033-01","tags":["Third Party Advisory","US Government Resource"],"source":"ics-cert@hq.dhs.gov"},{"url":"https://rockwellautomation.custhelp.com/app/answers/answer_view/a_id/1129877/loc/en_US#__highlight","tags":["Permissions Required","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://us-cert.cisa.gov/ics/advisories/icsa-21-033-01","tags":["Third Party Advisory","US Government Resource"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-22659","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}