The cybersecurity company Kaspersky detected almost 900 servers being compromised by sophisticated attackers leveraging the critical Zimbra Collaboration Suite (ZCS), which at the time was a zero-day without a patch for nearly 1.5 months.
“We investigated the threat and was able to confirm that unknown APT groups have actively been exploiting this vulnerability in the wild, one of which is systematically infecting all vulnerable servers in Central Asia”, Kaspersky
Zimbra Collaboration Suite (ZCS) Vulnerability
The vulnerability tracked as (CVE-2022-41352) is a remote code execution flaw that allows attackers to send an email with a malicious archive attachment that plants a web shell in the ZCS server while, at the same time, bypassing antivirus checks.
Kaspersky researchers say that various APT (advanced persistent threat) groups actively exploited the flaw soon after it was reported on the Zimbra forums.
Reports say a proof of concept for this vulnerability was added to the Metasploit framework, laying the groundwork for massive and global exploitation from even low-sophistication attackers.
Patch Available for the Vulnerability
Zimbra released a patch for this vulnerability; With ZCS version 9.0.0 P27, replacing the vulnerable component (cpio) with Pax and removing the weak part that made exploitation possible. Hence, update your devices immediately.
Researchers say performing disinfection on Zimbra is extremely difficult, since the attacker had access to configuration files containing passwords used by various service accounts.
Therefore, these credentials can be used to regain access to the server if the administrative panel is accessible from the internet.
Volexity stated that they identified approximately 1,600 ZCS servers that they believe were compromised by threat actors leveraging CVE-2022-41352 to plant webshells.
Reports say the initial attacks started in September, targeting vulnerable Zimbra servers in India and some in Turkey. Therefore, it was probably a testing wave against low-interest targets to assess the effectiveness of the attack.
Notably, Kaspersky assessed that the threat actors compromised 44 servers during this initial wave. Later on the threat actors began to carry out mass targeting to compromise as many servers worldwide before admins patched the systems and close the door to intruders.
At present, the second wave had a greater impact, infecting 832 servers with malicious webshells. Hence, it is recommended to update your devices immediately.
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