Last Modified: Apr 28, 2025
Affected Product(s):
BIG-IP LTM
Known Affected Versions:
11.5.4, 11.5.4 HF1, 11.5.4 HF2, 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, 12.0.0, 12.0.0 HF1, 12.0.0 HF2, 12.0.0 HF3, 12.0.0 HF4, 12.1.0, 12.1.0 HF1, 12.1.0 HF2, 12.1.1, 12.1.1 HF1, 12.1.1 HF2
Fixed In:
13.0.0, 12.1.2, 11.6.1 HF2, 11.5.4 HF3
Opened: Jul 19, 2016 Severity: 2-Critical Related Article:
K34302551
The debug TMM will produce a core on the assert "cwnd or ssthresh too low" when receiving an ICMP PMTUD packet with an MTU larger than the current MTU. This does not affect the default TMM.
Debug TMM crashes on assert "cwnd or ssthresh too low." Traffic disrupted while tmm restarts.
While using the debug TMM, an ICMP PMTUD packet is received with an MTU larger than the current MTU.
Block incoming ICMP PMTUD packets. Note that this will cause Path MTU Discovery to fail, and IP packets sent by the BIG-IP system with the Don't Fragment (DF) bit set may be dropped silently if the MTUs of the devices on the path are configured incorrectly.
The system now always updates TCP MSS after an ICMP PMTUD packet, so there is no debug TMM core.