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8 Known issues

Upgrade with MariaDB 10.2.1 and before

Upgrading Zabbix may fail if database tables were created with MariaDB 10.2.1 and before, because in those versions the default row format is compact. This can be fixed by changing the row format to dynamic (see also ZBX-17690).

NetBSD 8.0 and newer

Various Zabbix processes may randomly crash on startup on the NetBSD versions 8.X and 9.X. That is due to the too small default stack size (4MB), which must be increased by running:

ulimit -s 10240

For more information, please see the related problem report: ZBX-18275.

Problems with pressing Enter in configuration forms

Affects Zabbix versions 3.0.0 - 3.0.4. Pressing Enter in a text field of a configuration form is known to result in various problems.

For instance, if you open the configuration form of a host with linked templates, then press Enter in any text field and update the form, template linkage is removed (items from the template remain).

Agent items

  • net.dns[] Zabbix agent item does not support IPv6 addresses in its first parameter.

IPMI checks

IPMI checks will not work with the standard OpenIPMI library package on Debian prior to 9 (stretch) and Ubuntu prior to 16.04 (xenial). To fix that, recompile OpenIPMI library with OpenSSL enabled as discussed in ZBX-6139.

SSH checks

Some Linux distributions like Debian, Ubuntu do not support encrypted private keys (with passphrase) if the libssh2 library is installed from packages. Please see ZBX-4850 for more details.

When using libssh 0.9.x on CentOS 8 with OpenSSH 8 SSH checks may occasionally report "Cannot read data from SSH server". This is caused by a libssh issue (more detailed report). The error is expected to have been fixed by a stable libssh 0.9.5 release. See also ZBX-17756 for details.

ODBC checks

  • MySQL unixODBC driver should not be used with Zabbix server or Zabbix proxy compiled against MariaDB connector library and vice versa, if possible it is also better to avoid using the same connector as the driver due to an upstream bug. Suggested setup:
PostgreSQL, SQLite or Oracle connector → MariaDB or MySQL unixODBC driver
       MariaDB connector → MariaDB unixODBC driver
       MySQL connector → MySQL unixODBC driver

Please see ZBX-7665 for more information and available workarounds.

  • XML data queried from Microsoft SQL Server may get truncated in various ways on Linux and UNIX systems.
  • It has been observed that using ODBC checks on CentOS 8 for monitoring Oracle databases using Oracle Instant Client for Linux causes the Zabbix server to crash. The issue can be solved by upgrading Oracle Instant Client to,, or 19. See also ZBX-18402.

HTTPS checks

Web scenarios using the https protocol and Zabbix agent checks net.tcp.service[https...] and net.tcp.service.perf[https...] may fail if the target server is configured to disallow TLS v1.0 protocol or below. Please see ZBX-9879 for more information and available workarounds.

Simple checks

There is a bug in fping versions earlier than v3.10 that mishandles duplicate echo replay packets. This may cause unexpected results for icmpping, icmppingloss, icmppingsec items. It is recommended to use the latest version of fping. Please see ZBX-11726 for more details.

SNMP checks

If the OpenBSD operating system is used, a use-after-free bug in the Net-SNMP library up to the 5.7.3 version can cause a crash of Zabbix server if the SourceIP parameter is set in the Zabbix server configuration file. As a workaround, please do not set the SourceIP parameter. The same problem applies also for Linux, but it does not cause Zabbix server to stop working. A local patch for the net-snmp package on OpenBSD was applied and will be released with OpenBSD 6.3.

SNMP data spikes

Spikes in SNMP data have been observed that may be related to certain physical factors like voltage spikes in the mains. See ZBX-14318 more details.

SNMP traps

The "net-snmp-perl" package, needed for SNMP traps, has been removed in RHEL/CentOS 8.0-8.2; re-added in RHEL 8.3.

So if you are using RHEL 8.0-8.2, the best solution is to upgrade to RHEL 8.3; if you are using CentOS 8.0-8.2, you may wait for CentOS 8.3 or use a package from EPEL.

Please also see ZBX-17192 for more information.

Web monitoring

Zabbix server leaks memory on CentOS 6, CentOS 7 and possibly other related Linux distributions due to an upstream bug when "SSL verify peer" is enabled in web scenarios. Please see ZBX-10486 for more information and available workarounds.

Alerter process crash in Centos/RHEL 7

Instances of a Zabbix server alerter process crash have been encountered in Centos/RHEL 7. Please see ZBX-10461 for details.

Flipping frontend locales

It has been observed that frontend locales may flip without apparent logic, i. e. some pages (or parts of pages) are displayed in one language while other pages (or parts of pages) in a different language. Typically the problem may appear when there are several users, some of whom use one locale, while others use another.

A known workaround to this is to disable multithreading in PHP and Apache.

The problem is related to how setting the locale works in PHP: locale information is maintained per process, not per thread. So in a multi-thread environment, when there are several projects run by same Apache process, it is possible that the locale gets changed in another thread and that changes how data can be processed in the Zabbix thread.

For more information, please see related problem reports:

  • ZBX-10911 (Problem with flipping frontend locales)
  • ZBX-16297 (Problem with number processing in graphs using the bcdiv function of BC Math functions)

Compatibility issue with PHP 7.0

It has been observed that with PHP 7.0 importing a template with web monitoring triggers may fail due to incorrectly added double quotes to the web monitoring items in the trigger expressions. The issue goes away when upgrading PHP to 7.1.

MariaDB row size error

Prior to MariaDB 10.2.26, 10.3.17, and 10.4.7, MariaDB didn't properly calculate the row sizes while executing DDL, so "unsafe" tables could be created, even with innodb_strict_mode=ON set. This was fixed by MDEV-19292. As a side effect, tables that could be created in previous versions may get rejected after the latest releases.

Suggested database changes for existing 3.0 installations:

shell> mysql -uroot -p<password>
       mysql> alter table `host_inventory` modify `name` varchar(128) default '' not null, modify `alias` varchar(128) default '' not null, modify `os` varchar(128) default '' not null, modify `os_short`   varchar(128) default '' not null;

Suggested database changes for new 3.0 installations:

shell> mysql -uroot -p<password>
       mysql> set global innodb_strict_mode='OFF';

Perform database creation as usual and fix schema after:

shell> mysql -uroot -p<password>
       mysql> alter table `host_inventory` modify `name` varchar(128) default '' not null, modify `alias` varchar(128) default '' not null, modify `os` varchar(128) default '' not null, modify `os_short` varchar(128) default '' not null;
       mysql> set global innodb_strict_mode='ON';


Changes to Daylight Saving Time (DST) result in irregularities when displaying X axis labels (date duplication, date missing, etc).

Non-ASCII characters are incorrectly saved in MySQL

Affects Zabbix versions 3.0.0, 3.0.1 and 3.0.2 using MySQL database. Issue occurs when Zabbix server or proxy reads, processes and saves back to the database text containing non-ASCII characters (automatic template linking, low-level discovery, notification messages, …) The issue is transient, it is related to MySQL automatic reconnection behaviour. Fixed in 3.0.3rc1, ZBX-10540 contains patch and more information on the issue.

Log file monitoring

log[] and logrt[] items repeatedly reread log file from the beginning if file system is 100% full and the log file is being appended (see ZBX-10884 for more information).

Slow MySQL queries

Zabbix server generates slow select queries in case of non-existing values for items. This is caused by a known issue in MySQL 5.6/5.7 versions. A workaround to this is disabling the index_condition_pushdown optimizer in MySQL. For an extended discussion, see ZBX-10652.

API fails decoding valid JSON-RPC request

Affects Zabbix versions 3.0.4, 3.0.5. API fails to decode a valid JSON-RPC request unless a non-requirement php-json module is installed. ZBX-11244 contains more information on this issue.


Several operations can be assigned to the same step. If these operations have different step duration defined, the shortest one is taken into account and applied to the step. But due to bug there was exception to this rule when step duration is set to 0, it would use default value instead of shortest one. Now there will be no exception and default step duration will only be used if it's shortest, this is equivalent to behavior that frontend shows and user expects. Affects all versions, fixed in 3.0.7rc1, (see ZBX-11534 for more information).


The output parameter does not work properly with the history.get method.

API login

A large number of open user sessions can be created when using custom scripts with the user.login method without a following user.logout.

IPv6 address issue in SNMPv3 traps

Due to a net-snmp bug, IPv6 address may not be correctly displayed when using SNMPv3 in SNMP traps. For more details and a possible workaround, see ZBX-14541.

Zabbix agent checks on Windows

Non-existing DNS entries in a Server parameter of Zabbix agent configuration file (zabbix_agentd.conf) may increase Zabbix agent response time on Windows. This happens because Windows DNS caching daemon doesn't cache negative responses for IPv4 addresses. However, for IPv6 addresses negative responses are cached, so a possible workaround to this is disabling IPv4 on the host.

Known issues for 3.0.0 - 3.0.17

  • Remote commands executed on Zabbix server are displayed with an initial : colon in ReportsAction log.

Known issues for 3.0.0 - 3.0.18

  • When proc.mem, proc.num agent items are invoked from the command line and contain a command line parameter (e.g. using the agent test mode: zabbix_agentd -t proc.num[,,,apache2]), two extra processes are counted, as the agent counts itself twice.

Known issues for 3.0.18

  • 3.0.18 version Zabbix servers are not backwards (or forwards) compatible with 3.0.x proxies. Fixed for 3.0.19 Zabbix server.

Known issues for 3.0.0 - 3.0.24

Known issues starting with 3.0.25

  • Failed login attempt message has been changed to display only the first 39 characters of a stored IP address as that's the character limit in the database field. That means that IPv6 IP addresses longer than 39 characters will be shown incompletely.