CVE-2021-22659
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.
Does this matter?
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.
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.
- CVSS 3.1
- 8.6 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
- EPSS
- 1.80% probability · 78th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-120
- Affected
- rockwellautomation/micrologix 1400 firmware
- Source
- ics-cert@hq.dhs.gov
EPSS 1.8% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://rockwellautomation.custhelp.com/app/answers/answer_view/a_id/1129877/loc/en_US#__highlightPermissions Required, Vendor Advisory
- https://us-cert.cisa.gov/ics/advisories/icsa-21-033-01Third Party Advisory, US Government Resource
- https://rockwellautomation.custhelp.com/app/answers/answer_view/a_id/1129877/loc/en_US#__highlightPermissions Required, Vendor Advisory
- https://us-cert.cisa.gov/ics/advisories/icsa-21-033-01Third Party Advisory, US Government Resource
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.