Bug ID 1012581: Evidence of hardware syncookies triggered but no stats after tcp half-open is triggered

Last Modified: Sep 23, 2021

Bug Tracker

Affected Product:  See more info
BIG-IP AFM(all modules)

Known Affected Versions:
14.1.0,,,,,, 14.1.2,,,,,,,,, 14.1.3,, 14.1.4,,,,, 15.0.0, 15.0.1,,,,, 15.1.0,,,,,, 15.1.1, 15.1.2,, 15.1.3,, 15.1.4, 16.0.0,, 16.0.1,,, 16.1.0

Opened: Apr 20, 2021
Severity: 3-Major


As soon as global syncookie enabled stats counts starts decrementing and when attack_detection_common callback function calls, the stats range is always under the configured packets per-second threshold, resulting in some tmms not being able to detect the attack but syncookies are already enabled on these tmms, and no statistics are gathered.


SYN cookies may still be sent after traffic goes below the attack detection threshold.


A SYN flood attack or similar SYN attack where SYNs are flooded into the BIG-IP system.


Restart tmm

Fix Information


Behavior Change