CVE-2022-31138 is a vulnerability classified under CWE-78, which pertains to improper neutralization of special elements used in OS commands, commonly known as OS Command Injection. This vulnerability affects mailcow-dockerized, a popular mail server suite deployed in containerized environments. Specifically, versions prior to 2022-06a are vulnerable. The issue arises from insufficient sanitization of user-controllable parameters such as regexmess, skipmess, regexflag, delete2foldersonly, delete2foldersbutnot, regextrans2, pipemess, and maxlinelengthcmd. By manipulating these parameters, an attacker with appropriate privileges can inject arbitrary OS commands, leading to code execution with extended privileges. This can allow an attacker to execute commands on the host system, potentially compromising the mail server and any data or services it manages. The vulnerability is mitigated in version 2022-06a and later, where proper input validation and sanitization have been implemented. Until the patch is applied, a temporary workaround involves removing the Syncjob Access Control List (ACL) from all mailbox users, which prevents them from modifying the vulnerable settings. There are no known exploits in the wild as of the published date, but the nature of the vulnerability makes it a significant risk if exploited. The attack vector requires authenticated access with permissions to modify the affected parameters, which somewhat limits the attack surface but does not eliminate risk, especially in environments with multiple users or weak authentication controls.

For European organizations, the exploitation of this vulnerability could lead to unauthorized code execution on mail servers, resulting in potential data breaches, disruption of email services, and lateral movement within the network. Given that mailcow is used by various organizations for managing email infrastructure, a successful attack could compromise sensitive communications, expose confidential information, and degrade operational availability. The impact extends beyond confidentiality to integrity and availability, as attackers could alter mail processing rules, delete or reroute emails, or disrupt mail services entirely. This could have severe consequences for businesses, government agencies, and critical infrastructure operators relying on mailcow for secure and reliable email services. Additionally, the ability to execute arbitrary commands with elevated privileges could allow attackers to establish persistent footholds, deploy malware, or pivot to other internal systems, amplifying the overall risk. The medium severity rating reflects the requirement for authenticated access and specific permissions, but the potential for significant damage if exploited remains high.

European organizations using mailcow-dockerized should immediately update their installations to version 2022-06a or later using the official `update.sh` script provided in the mailcow root directory. This update addresses the input validation flaws and neutralizes the command injection vectors. Until the update can be applied, administrators should remove the Syncjob ACL from all mailbox users to prevent modification of the vulnerable parameters, effectively blocking exploitation attempts. Additionally, organizations should audit user permissions to ensure that only trusted users have access to modify mailcow settings, implement strong authentication mechanisms such as multi-factor authentication (MFA), and monitor logs for unusual activities related to parameter changes or command execution. Network segmentation of mail servers and application of strict firewall rules can further reduce exposure. Regular backups of mail server configurations and data should be maintained to enable recovery in case of compromise. Finally, organizations should stay informed about any emerging exploit reports or patches related to this vulnerability.