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, 11.5.3, 11.5.3 hf1, 11.5.3 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, 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, 11.5.4
Opened: Mar 26, 2015 Severity: 3-Major Related Article:
K17144
TMM cores and memory exhaustion using Direct Server Return (DSR). DSR establishes a one-way tunnel between the BIG-IP system and the back-end servers using the clients' IP addresses as the tunnel local-address on the BIG-IP system. These flows never expire.
Server-side DSR tunnel flow never expires. Because the DSR tunnels use client's IP address as the tunnel local-address and the server's IP address as the tunnel remote-address, a single DSR setup might introduce as many tunnels as the clients' requests. When these tunnels do not expire, the BIG-IP system memory resource might be used up eventually, causing TMM cores. Traffic disrupted while tmm restarts.
BIG-IP virtual servers using DSR tunnels to send client traffic to the server.
None.
Individual DSR tunnels are removed after the corresponding client's user flows expire.