A Predictable Value Range from Previous Values issue was discovered in Rockwell Automation Allen-Bradley MicroLogix 1100 programmable-logic controllers 1763-L16AWA, Series A and B, Version 16.00 and prior versions; 1763-L16BBB, Series A and B, Version 16.00 and prior versions; 1763-L16BWA, Series A and B, Version 16.00 and prior versions; and 1763-L16DWD, Series A and B, Version 16.00 and prior versions and Allen-Bradley MicroLogix 1400 programmable logic controllers 1766-L32AWA, Series A and B, Version 16.00 and prior versions; 1766-L32BWA, Series A and B, Version 16.00 and prior versions; 1766-L32BWAA, Series A and B, Version 16.00 and prior versions; 1766-L32BXB, Series A and B, Version 16.00 and prior versions; 1766-L32BXBA, Series A and B, Version 16.00 and prior versions; and 1766-L32AWAA, Series A and B, Version 16.00 and prior versions. Insufficiently random TCP initial sequence numbers are generated, which may allow an attacker to predict the numbers from previous values. This may allow an attacker to spoof or disrupt TCP connections, resulting in a denial of service for the target device.
Weakness
The product’s random number generator produces a series of values which, when observed, can be used to infer a relatively small range of possibilities for the next value that could be generated.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| 1763-l16awa_series_a | Rockwellautomation | * | 16.000 (including) |
| 1763-l16awa_series_b | Rockwellautomation | * | 16.000 (including) |
| 1763-l16bbb_series_a | Rockwellautomation | * | 16.000 (including) |
| 1763-l16bbb_series_b | Rockwellautomation | * | 16.000 (including) |
| 1763-l16bwa_series_a | Rockwellautomation | * | 16.000 (including) |
| 1763-l16bwa_series_b | Rockwellautomation | * | 16.000 (including) |
| 1763-l16dwd_series_a | Rockwellautomation | * | 16.000 (including) |
| 1763-l16dwd_series_b | Rockwellautomation | * | 16.000 (including) |