All Zimbra administrators should make sure the pax package is installed on their Zimbra server. Pax is needed by Amavis to extract the contents of compressed attachments for virus scanning. If the pax package is not installed, Amavis will fall-back to using cpio, unfortunately the fall-back is implemented poorly (by Amavis) and will allow an […]
Archive | Security & Privacy
Configuring Fail2Ban on Zimbra
This article is a how-to guide on installing Fail2Ban to block attacking hosts using a null route or blackhole routes. This can help mitigate brute force attacks on Zimbra. Especially brute force attacks on SMTP are very common. Prerequisite: Fail2ban has been tested in combination with netfilter-persistent and iptables. If you use ufw or firewalld […]
Authentication Bypass in MailboxImportServlet vulnerability
Zimbra 8.8.15 patch 33 and Zimbra 9.0.0 patch 26 contain an important security update that fixes an authentication bypass in MailboxImportServlet (CVE-2022-37042 and CVE-2022-27925). If you are running a Zimbra version that is older than Zimbra 8.8.15 patch 33 or Zimbra 9.0.0 patch 26 you should update to the latest patch as soon as possible. […]
Zimbra with Let’s Encrypt Certificates a step-by-step guide (update)
By Barry de Graaff on August 10, 2022 in Community, Security & Privacy, Zimbra Server, Zimbra SkillZ
This article is a step-by-step instruction on setting up a Zimbra with Let’s Encrypt certificates. If you are running a multi server installation of Zimbra it is recommended you set-up a dedicated VM for obtaining the Let’s Encrypt certificate and follow this blog. Prerequisites This guide assumes you are using Ubuntu 20 and you have […]
Deprecation of the “X-XSS-Protection” header
Hello Zimbra Customers, Partners & Friends, In the past Zimbra recommended to set the X-XSS-Protection HTTP response header. This header used to enable additional protection against cross-site scripting (XSS) attacks in some web browsers. However this header is now deprecated and support is removed from most browsers. In case you have configured Zimbra to use […]
Implementing Custom Authentication using a Zimbra extension (updated)
By Barry de Graaff on June 15, 2022 in Community, Open Source, Security & Privacy, Zimbra SkillZ, Zimlets
In this article you will learn how to implement Custom Authentication using a Zimbra extension. The Java project and source code can be found at https://github.com/Zimbra/zimbra-custom-authentication. Take a look at https://github.com/Zimbra/zm-extension-guide if you are new to Java or building Zimbra extensions. The zm-extension-guide covers all the things needed to build the Custom Authentication extension. Zimbra […]