Description

Libraesva has released a critical security advisory regarding a command injection vulnerability, identified as CVE-2025-59689, affecting its Email Security Gateway (ESG) software from version 4.5 onwards. The flaw allows attackers to send specially crafted compressed attachments via email to execute arbitrary shell commands under a non-privileged user. The root cause lies in insufficient sanitization when removing active code from files within certain compressed archive formats, enabling attackers to bypass input validation. The vulnerability has already been exploited in at least one confirmed incident, which was highly targeted and attributed to a hostile state actor. Researchers noted the precision of the attack, which focused on a single ESG appliance suggesting a case of cyber espionage rather than a widespread financial threat. While the vulnerability does not grant immediate administrative access, it can still be used as a foothold for persistence, lateral movement, or privilege escalation within affected environments. Libraesva has released patches for all affected 5.x versions, with fixes included in versions 5.0.31, 5.1.20, 5.2.31, 5.4.8, and 5.5.7. Cloud-based ESG instances have already been updated, and on-premise 5.x systems have received automatic updates. However, customers running unsupported 4.x versions must upgrade manually to ensure protection. Libraesva urges all users to verify their ESG version and apply updates immediately to mitigate the risk of exploitation.