Bug ID 749675: DNS cache resolver may return a malformed truncated response with multiple OPT records

Last Modified: Sep 13, 2023

Affected Product(s):
BIG-IP DNS, GTM(all modules)

Known Affected Versions:
11.5.5, 11.5.6, 11.5.7, 11.6.0, 11.6.1, 11.6.2, 11.6.3,,,, 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, 13.0.1, 13.1.0,,,,,,,,, 13.1.1,,, 14.0.0,,,, 14.1.0

Fixed In:
15.0.0,,,, 12.1.4,, 11.5.8

Opened: Nov 14, 2018

Severity: 3-Major


A configured DNS resolving cache returns a response with two OPT records when the response is truncated and not in the cache.


A DNS message with multiple OPT records is considered malformed and will likely be dropped by the client.


This can occur when: -- A DNS resolving cache is configured. -- The DNS query being handled is not already cached. -- The response for the query must be truncated because it is larger than the size the client can handle (either 512 bytes or the buffer size indicated by an OPT record in the query).


A second query will return the cached record, which will only have one OPT record.

Fix Information

DNS cache resolver now returns the correct response under these conditions.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips