Last Modified: Aug 19, 2026
Affected Product(s):
BIG-IP GTM, LTM
Known Affected Versions:
11.5.3, 11.5.3 hf1, 11.5.3 hf2, 11.5.4, 11.5.4 hf1, 11.5.4 hf2, 11.5.4 hf3, 11.5.4 hf4, 11.5.5, 11.5.6, 11.5.7, 11.5.8, 11.5.9, 11.5.10, 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, 12.0.0, 12.0.0 hf1, 12.0.0 hf2, 12.0.0 hf3, 12.0.0 hf4
Fixed In:
12.1.0, 11.6.1
Opened: Oct 29, 2015 Severity: 2-Critical
A resolver sending a query with a small EDNS0 UDP buffer limit can lead to packet truncation. These response packets are flagged as truncated in the header, but the OPT record might be cut/missing leading some resolvers to consider the packet malformed.
Some resolvers regard OPT-less truncated packets as malformed and cease follow-up requests via TCP or a larger EDNS0 UDP limit.
Primarily via dynamic settings such as iRules on DNS_RESPONSE events adding new records, or DNSSEC record signing with responses over UDP.
none
Truncated DNSSEC or iRule DNS packets are RFC-compliant.