Bug ID 686065: RESOLV::lookup iRule command can trigger crash with slow resolver

Last Modified: Sep 13, 2023

Affected Product(s):
BIG-IP LTM(all modules)

Known Affected Versions:
12.0.0, 12.0.0 HF1, 12.1.0 HF1, 12.0.0 HF2, 12.1.0 HF2, 12.0.0 HF3, 12.0.0 HF4, 12.1.1 HF1, 12.1.1 HF2, 12.1.2 HF1, 12.1.2 HF2, 12.1.0, 12.1.1, 12.1.2, 12.1.3,, 13.0.0, 13.0.0 HF1, 13.0.0 HF2, 13.0.0 HF3, 13.1.0,,,

Fixed In:
14.0.0,, 13.0.1,

Opened: Sep 28, 2017

Severity: 3-Major


If thousands of connections are serviced by an iRule that performs a lookup for the same FQDN before the FQDN can be resolved, tmm may crash.


Traffic disrupted while tmm restarts.


iRule with RESOLV::lookup. Slow DNS resolver. Thousand of connections triggering resolution of the same name.


Remove RESOLV::lookup from the workflow if it is not required.

Fix Information

The scenario now works as expected and no longer results in a crash.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips