Bug ID 942793: BIG-IP system cannot accept STARTTLS command with trailing white space

Last Modified: Oct 05, 2023

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

Known Affected Versions:
14.1.0,,,,,, 14.1.2,,,,,,,,, 14.1.3,, 14.1.4,,,,,,, 14.1.5,,,,,, 15.0.0, 15.0.1,,,,, 15.1.0,,,,,, 15.1.1, 15.1.2,, 15.1.3,, 15.1.4,, 15.1.5,, 15.1.6,, 15.1.7, 15.1.8,,, 15.1.9,, 15.1.10,, 16.0.0,, 16.0.1,,

Fixed In:

Opened: Sep 05, 2020

Severity: 4-Minor


When an SMTPS profile is applied on a virtual server and the SMTP client sends a STARTTLS command containing trailing white space, the BIG-IP system replies with '501 Syntax error'. The command is then forwarded to the pool member, which can result in multiple error messages being sent to the SMTP client.


The SMTP client is unable to connect to the SMTP server.


-- A virtual server is configured with an SMTPS profile. -- The SMTP client sends a STARTTLS command with trailing spaces.


Use an SMTP client that does not send a command containing trailing white space.

Fix Information

The system now handles trailing white spaces in SMTP STARTTLS command.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips