CVE-2025-3928 is a critical vulnerability in the Commvault Web Server component, identified in multiple versions before 11.36.46, 11.32.89, 11.28.141, and 11.20.217, affecting both Windows and Linux platforms. The vulnerability allows a remote attacker with valid authentication credentials to create and execute webshells on the server. Webshells provide attackers with a persistent foothold, enabling them to execute arbitrary commands, escalate privileges, exfiltrate sensitive data, and disrupt services. The CVSS v3.1 score of 8.8 reflects the high impact on confidentiality, integrity, and availability, with low attack complexity and no user interaction required. The vulnerability is significant because it targets backup infrastructure, which often holds critical organizational data and access to broader network environments. The Commvault advisory highlights the risk of webserver compromise through malicious webshell deployment, a common technique in advanced persistent threats. Although no public exploits are currently known, the inclusion in the CISA Known Exploited Vulnerabilities Catalog signals that exploitation attempts are anticipated or ongoing. The vulnerability affects multiple widely deployed versions, necessitating urgent patching and monitoring to prevent exploitation.

For European organizations, exploitation of CVE-2025-3928 could lead to severe consequences including unauthorized access to sensitive backup data, disruption of backup and recovery operations, and potential lateral movement within networks. This could result in data breaches, loss of data integrity, and operational downtime impacting business continuity. Given the critical role of backup systems in disaster recovery and compliance, successful exploitation could also lead to regulatory penalties under GDPR if personal data is compromised. Organizations in sectors such as finance, healthcare, government, and critical infrastructure are particularly at risk due to their reliance on Commvault solutions and the sensitivity of their data. The ability to execute webshells remotely with authenticated access increases the risk of stealthy, persistent attacks that are difficult to detect and remediate. The impact extends beyond individual organizations to supply chains and service providers using Commvault, potentially amplifying the threat across European digital ecosystems.

1. Immediately upgrade Commvault Web Server installations to the fixed versions 11.36.46, 11.32.89, 11.28.141, or 11.20.217 depending on the current version and platform. 2. Enforce strict access controls and multi-factor authentication (MFA) for all users with access to Commvault web interfaces to reduce the risk of credential compromise. 3. Implement network segmentation to isolate backup infrastructure from general user networks and limit exposure to authenticated attackers. 4. Deploy web application firewalls (WAFs) and intrusion detection/prevention systems (IDS/IPS) tuned to detect webshell signatures and anomalous webserver behavior. 5. Conduct regular audits and monitoring of webserver logs and file system changes to identify unauthorized webshell creation or execution. 6. Educate administrators on secure configuration best practices and the importance of timely patching. 7. Develop and test incident response plans specifically addressing webshell detection and removal in backup environments. 8. Collaborate with Commvault support and threat intelligence providers to stay informed about emerging exploit techniques and indicators of compromise.