CVE 2021-22681 https://www.rockwellautomation.com/en-us/trust-center/security-advisories/advisory.PN1550.html  and send a specially crafted CIP message to the device. If exploited, a threat actor could help prevent access to the legitimate user and end connections to connected devices including the workstation. To recover the controllers, a download is required which ends any process that the controller is running.

A denial-of-service vulnerability exists in the Rockwell Automation affected products when specially crafted packets are sent to the CIP Security Object. If exploited the device will become unavailable and require a factory reset to recover.

An unauthorized user could use a specially crafted sequence of Ethernet/IP messages, combined with heavy traffic loading to cause a denial-of-service condition in Rockwell Automation Logix controllers resulting in a major non-recoverable fault. If the target device becomes unavailable, a user would have to clear the fault and redownload the user project file to bring the device back online and continue normal operation.

A vulnerability exists in the Rockwell Automation controllers that allows a malformed CIP request to cause a major non-recoverable fault (MNRF) and a denial-of-service condition (DOS).

The connection establishment algorithm found in Rockwell Automation CompactLogix 5370 and ControlLogix 5570 versions 33 and prior does not sufficiently manage its control flow during execution, creating an infinite loop. This may allow an attacker to send specially crafted CIP packet requests to a controller, which may cause denial-of-service conditions in communications with other products.

A malformed Class 3 common industrial protocol message with a cached connection can cause a denial-of-service condition in Rockwell Automation Logix Controllers, resulting in a major nonrecoverable fault. If the target device becomes unavailable, a user would have to clear the fault and redownload the user project file to bring the device back online.

Rockwell Automation Studio 5000 Logix Designer (all versions) are vulnerable when an attacker who achieves administrator access on a workstation running Studio 5000 Logix Designer could inject controller code undetectable to a user.

An attacker with the ability to modify a user program may change user program code on some ControlLogix, CompactLogix, and GuardLogix Control systems. Studio 5000 Logix Designer writes user-readable program code to a separate location than the executed compiled code, allowing an attacker to change one and not the other.

An attacker could send a crafted HTTP/HTTPS request to render the web server unavailable and/or lead to remote code execution caused by a stack-based buffer overflow vulnerability. A cold restart is required for recovering CompactLogix 5370 L1, L2, and L3 Controllers, Compact GuardLogix 5370 controllers, and Armor Compact GuardLogix 5370 Controllers Versions 20 - 30 and earlier.

An attacker could send crafted SMTP packets to cause a denial-of-service condition where the controller enters a major non-recoverable faulted state (MNRF) in CompactLogix 5370 L1, L2, and L3 Controllers, Compact GuardLogix 5370 controllers, and Armor Compact GuardLogix 5370 Controllers Versions 20 - 30 and earlier.