Last Modified: Aug 19, 2026
Affected Product(s):
BIG-IP LTM
Known Affected Versions:
11.5.1, 11.5.1 hf1, 11.5.1 hf2, 11.5.1 hf3, 11.5.1 hf4, 11.5.1 hf5, 11.5.1 hf6, 11.5.1 hf7, 11.5.1 hf8, 11.5.1 hf9, 11.5.1 hf10, 11.5.1 hf11, 11.5.2, 11.5.2 hf1, 11.6.0, 11.6.0 hf1, 11.6.0 hf2, 11.6.0 hf3, 11.6.0 hf4, 11.6.0 hf5, 11.6.0 hf6, 11.6.0 hf7, 11.6.0 hf8, 11.6.1, 11.6.1 hf1, 11.6.1 hf2, 11.6.2, 11.6.2 hf1, 11.6.3, 11.6.3.1, 11.6.3.2, 11.6.3.3, 11.6.3.4, 11.6.4, 11.6.5, 11.6.5.1, 11.6.5.2, 11.6.5.3
Fixed In:
12.0.0, 11.5.3
Opened: Oct 20, 2014 Severity: 3-Major Related Article:
K16046
iRule 'virtual' command allows for protocol mismatch.
tmm might crash with assert: 'Must be syncookie'. Traffic is interrupted.
A virtual server with an iRule which leverages the 'virtual' command targeting a virtual server that differs in protocol. For example, a UDP virtual server targeting a TCP virtual server.
This is the result of a misconfiguration. Modify iRules to ensure L4 protocols match between virtual servers.
Resolved issue where TMM might crash with assert: 'Must be syncookie' when the iRule 'virtual' command leads to a protocol mismatch.