Threat actors have started exploiting a recently patched critical-severity vulnerability in VMware vCenter, rapid incident response company Quirso reports.
The bug was disclosed on July 29, when Broadcom patched it alongside four other security defects in multiple VMware products.
Tracked as CVE-2026-59310 (CVSS score of 9.8), the flaw is described as a directory traversal issue in the Syslog server that leads to remote code execution.
“A malicious actor with network access to vCenter may exploit this issue to execute arbitrary code,” Broadcom’s advisory reads.
According to Quirso, an advanced persistent threat (APT) actor has been exploiting web-accessible VMware vCenter servers vulnerable to CVE-2026-59310, using a reverse shell for persistent access.
The cybersecurity company identified over 360 victim IP addresses across 47 countries, half of which are distributed across only five countries: Germany, the US, Turkey, Iran, and France.
“The exact number of victim organizations cannot be inferred from these IP addresses, as an IP address does not necessarily correspond to a unique company or physical system. Some addresses belong to hosting providers, cloud networks, or shared infrastructure,” Quirso says.
According to the company, the exploitation started on August 3, with over 340 victim IP addresses seen connecting to the attackers’ infrastructure by August 5.
“While the attacker might have had prior knowledge of the vulnerability, the strong correlation between the time of disclosure and exploitation suggests the disclosure as the initial starting point for the campaign,” Quirso notes.
Following initial compromise, the attackers dropped the open source SSH reverse shell framework reverse_ssh to maintain an outbound control connection from the compromised systems, bypassing security controls that typically block inbound connections.
Quirso released a generic YARA rule for identifying reverse_ssh builds. As the tool can also be used for legitimate penetration testing, organizations with publicly accessible vCenter systems are advised to validate any detections by also looking for unauthorized installations and unexpected outbound connections and execution.
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