CVE-2019-3396

Atlassian Confluence Server and Data Center contain a server-side template injection flaw (CWE-22) in which attacker-supplied template content is processed by the server, enabling path traversal and ultimately remote code execution. An attacker triggers it by submitting crafted template syntax in a request to a vulnerable instance, and can run arbitrary commands or code on the underlying server. Successful compromise could allow data theft, deployment of webshells, or ransomware; CISA notes known ransomware use of this vulnerability. Organizations running self-hosted Confluence Server or Data Center are affected, particularly instances exposed to the internet. Exploitation is confirmed in the wild: the flaw is in CISA's Known Exploited Vulnerabilities catalog (added 2021-11-03) and EPSS assigns a 99.9% probability of exploitation, placing it in the top percentile.

What to do: Apply updates per vendor instructions by upgrading Confluence Server and Data Center to Atlassian's fixed releases, and prioritize internet-facing instances. Until patched, restrict network exposure of Confluence and monitor for signs of compromise such as webshells, unexpected processes, or ransomware activity, since ransomware operators are known to exploit this flaw.