Over 80,000 servers hit as Roundcube RCE bug gets rapidly exploited

Threat actors exploited a critical remote code execution (RCE) flaw in Roundcube, tracked as CVE-2025-49113, just days after the patch was released, targeting over 80,000 servers.

Roundcube is a popular webmail platform and has been repeatedly targeted by advanced threat groups like APT28 and Winter Vivern. In the past, attackers exploited these vulnerabilities to steal login credentials and spy on sensitive communications. These campaigns show how unpatched systems remain at serious risk, especially for high-value targets.

Last week, the critical flaw CVE-2025-49113 (CVSS score of 9.9) was discovered after it had gone unnoticed for over a decade. An attacker can exploit the flaw to take control of affected systems and run malicious code, putting users and organizations at significant risk. Kirill Firsov, founder and CEO of FearsOff, discovered the vulnerability.

“Roundcube Webmail before 1.5.10 and 1.6.x before 1.6.11 allows remote code execution by authenticated users because the _from parameter in a URL is not validated in program/actions/settings/upload.php, leading to PHP Object Deserialization.” reads the advisory published by NIST.

To read the complete article see: Security Affairs