Bug ID 904053: Unable to set ASM Main Cookie/Domain Cookie hashing to Never

Last Modified: Nov 23, 2020

Bug Tracker

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

Known Affected Versions:
13.1.0, 13.1.0.1, 13.1.0.2, 13.1.0.3, 13.1.0.4, 13.1.0.5, 13.1.0.6, 13.1.0.7, 13.1.0.8, 13.1.1, 13.1.1.2, 13.1.1.3, 13.1.1.4, 13.1.1.5, 13.1.3, 13.1.3.1, 13.1.3.2, 13.1.3.3, 13.1.3.4, 14.0.0, 14.0.0.1, 14.0.0.2, 14.0.0.3, 14.0.0.4, 14.0.0.5, 14.0.1, 14.0.1.1, 14.1.0, 14.1.0.1, 14.1.0.2, 14.1.0.3, 14.1.0.5, 14.1.0.6, 14.1.2, 14.1.2.1, 14.1.2.2, 14.1.2.3, 14.1.2.4, 14.1.2.5, 14.1.2.6, 14.1.2.7, 14.1.2.8, 15.0.0, 15.0.1, 15.0.1.1, 15.0.1.2, 15.0.1.3, 15.0.1.4, 15.1.0, 15.1.0.1, 15.1.0.2, 15.1.0.3, 15.1.0.4, 15.1.0.5, 15.1.1, 16.0.0, 16.0.0.1, 16.0.1

Fixed In:
15.1.2

Opened: Apr 26, 2020
Severity: 3-Major

Symptoms

Disabling ASM Main Cookie/Domain Cookie hashing in a Policy's Learning and Blocking Setting with 'Never (wildcard only)' does not stop the ASM Main Cookie from continuing to hash server-provided cookies.

Impact

A sufficient number of ASM Main Cookies and/or a sufficiently large number of cookies for each ASM Main cookie to hash can result in the HTTP header becoming prohibitively large, causing traffic to be refused by the server.

Conditions

-- ASM enabled. -- Learning mode enabled for Policy. -- Learn New Cookies set to 'Never (wildcard only)' instead of default 'Selective'.

Workaround

Disable Learning mode for the Policy disables Cookie hashing. Note: This affects all learning, not just Cookie hashing.

Fix Information

Cookie hashing can now be disabled at the policy level in the Cookie subsection of an ASM Policy's Learning and Blocking Settings by setting Learn New Cookies to "Never (wildcard only)".

Behavior Change