Proof of concept (PoC) code has been released for a cross-platform exploit that can be performed on unpatched Veeam Backup & Replication (VBR) software. Veeam are a data security organisation whose backup and recovery software is used as both on-premises and cloud-based data protection solutions. Security updates to patch the exploitable vulnerability were released earlier this month, as VBR versions V11a and V12. Any users who have not yet applied these updates are now at greater risk of attack after Horizon3 have released their deep dive into this vulnerability, including PoC exploit information that malicious actors could make use of. 

CVE-2023-27532 is a high severity vulnerability that exists in the Veeam.Backup.Service executable and affects all versions of Veeam Backup & Replication before the new V11a and V12 updates. This vulnerability allows unauthenticated attackers to access encrypted credentials stored in the configuration database. This can occur when the attackers are operating within the backup infrastructure network perimeter and can lead to access to the backup infrastructure hosts. The published exploit uses vulnerable TCP port 9401 to access the infrastructure, where credentials are then extracted as clear text. Attackers can then use these stolen credentials to gain the ability to perform remote code execution at the SYSTEM level.  

The vulnerable app is hosting a Windows Communication Foundation (WCF) service. This service uses a binary protocol built on TCP for the WCF to WCF communication, through the use of NetTcpBinding. The PoC exploit is written in .NET core language which allows for cross-platform functionality, so users on both Windows and Linux system are at risk of an attack, and should apply the security patches to their systems as soon as possible. Veeam’s security advisory also suggests a workaround for users who cannot apply the security upgrades or use an all-in-one appliance with no remote backup capabilities. Users can block external connections to the affected TCP port 9401 on the backup server firewall to prevent attackers from being able to gain access to the vulnerable system. This should be considered a temporary workaround and not a permanent fix, and the updates should be applied to fully resolve the vulnerability as soon as possible.