Bug ID 603723: TLS v1.0 fallback can be triggered intermittently and fail with restrictive server setup

Last Modified: Sep 13, 2023

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

Known Affected Versions:
11.6.0, 11.6.1, 11.6.2, 11.6.3,,,,, 11.6.4, 11.6.5,,,, 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

Fixed In:
13.0.0, 12.1.2 HF1, 11.5.4 HF3

Opened: Jul 08, 2016

Severity: 3-Major


HTTPS monitors mark a TLS v1.2-configured pool member down and never mark it back up again, even if the pool member is up. The monitor works normally until the SSL handshake fails for any reason. After the handshake fails, the monitor falls back to TLS v1.1, which the pool members reject, and the node remains marked down.


Once the handshake fails, the monitor remains in fallback mode and sends TLS v1.0 or TLS v1.1 requests to the pool member. The pool member remains marked down.


This might occur when the following conditions are met: -- Using HTTPS monitors. -- Pool members are configured to use TLS v1.2 only.



Fix Information

The system now successfully handles TLS v1.0 fallback when pool members are configured to use TLS v1.2 only, so pool members are correctly marked as being up.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips