CVE-2019-3396: Atlassian Confluence Server and Data Center Server-Side Template Injection Vulnerability

CVE-2019-3396 is a server-side template injection vulnerability in Atlassian Confluence Server and Data Center. According to CISA, it may allow an attacker to achieve path traversal and remote code execution. It has been used in ransomware activity, so unpatched instances remain a high-priority risk for IT and security teams.

Defenders should treat this as a serious remote code execution path on a widely deployed collaboration platform and confirm all version and fix details directly against the vendor advisory.

How it works

The weakness is tracked as CWE-22 (path traversal) in the context of a server-side template injection flaw. In products of this class, user-controlled input reaches a template engine without proper sanitization. An attacker who can supply crafted template expressions may cause the server to resolve unintended paths or evaluate code in the application’s context.

Successful abuse can lead to reading files outside intended directories and, as described by CISA, remote code execution on the Confluence host. Exact request patterns, parameters, and exploit mechanics are not detailed here; teams must rely on the vendor advisory and their own testing rather than public proof-of-concept material.

Am I affected? How to find it in your systems

Atlassian Confluence Server and Data Center typically run as internal or externally reachable web applications used for wikis, documentation, and team collaboration. They are often deployed on Linux or Windows servers, sometimes behind reverse proxies, and may be exposed to the internet for remote access.

Inventory steps:

• Identify all Confluence Server and Data Center instances via asset management, CMDB, or network scans for Confluence service banners and default ports.
• Record the installed version and edition from the administration console or installation directories; compare them only against the fixed versions listed in the vendor advisory.
• Note whether the instance is reachable from untrusted networks and whether anonymous or low-privilege access is enabled.
• Review web server, reverse-proxy, and Confluence application logs for unusual template-related requests, unexpected path patterns, or spikes in errors around the vulnerable component. Specific indicators of compromise should be validated against vendor or trusted threat-intelligence guidance.

If you cannot determine the version or exposure with certainty, assume the instance needs review until confirmed otherwise.

How to remediate

Patch first. Apply the updates published by Atlassian for Confluence Server and Data Center exactly as described in the vendor advisory. CISA’s required action is to apply updates per vendor instructions.

After patching:

• Restart services as directed and verify the new version is running.
• Restrict administrative interfaces to trusted networks and enforce strong authentication.
• Disable or tightly control any features that accept untrusted template or markup input if the advisory or hardening guides recommend it.
• Ensure the Confluence process runs with least privilege and that file-system permissions limit what the application account can read or write.
• Re-scan or re-inventory to confirm no remaining unpatched instances.

If you can't patch immediately

Implement compensating controls until the vendor update can be applied:

• Segment Confluence hosts so they are not reachable from the public internet or broad internal networks; allow access only from required client subnets via VPN or reverse proxy with authentication.
• Place a web application firewall or reverse-proxy rules in front of Confluence to block or challenge requests that match known exploitation patterns for this class of flaw; tune carefully to avoid breaking legitimate use and confirm signatures against current guidance.
• Temporarily disable or restrict the affected feature or endpoint if the vendor or your risk assessment allows it without breaking critical workflows.
• Increase monitoring: forward Confluence and proxy logs to a SIEM, alert on anomalous request volumes, unusual path strings, or post-authentication command activity, and ensure endpoint detection is active on the host.
• Reduce the attack surface by removing unnecessary plugins, anonymous access, and unused network listeners.

These measures reduce risk but do not replace the patch.

If your data may have been exposed

Actively exploited vulnerabilities of this type, including those with known ransomware use, frequently lead to full host compromise, data theft, and follow-on encryption or extortion. If you have evidence of exploitation or cannot rule it out, follow your incident-response process: isolate affected systems, preserve logs, rotate credentials, and assess what data the Confluence instance could access.

You can also run a free exposure scan of your email addresses against known breach data to check whether credentials or personal information associated with your organization have appeared in prior breaches, then force password resets and enable multi-factor authentication where needed.