CVE-2026-26190

Milvus, an open-source vector database for generative AI applications, exposes a metrics/management service on TCP port 9091 by default in versions prior to 2.5.27 and 2.6.10, and this port hosts both a fully unauthenticated REST API and a weakly protected debug endpoint. Remote attackers can call the entire /api/v1/* REST API with no credentials at all, and can invoke the /expr debug endpoint using a predictable default authentication token derived from the default etcd root path (by-dev), enabling arbitrary expression evaluation. Successful exploitation yields unauthenticated access to all business operations, including reading and modifying stored vector data and managing credentials, effectively a full compromise of the instance (CVSS 9.8 critical). Any deployment whose port 9091 is reachable by untrusted clients, which is typical of default Docker, container, and cloud configurations, is affected. No confirmed in-the-wild exploitation has been reported yet, but a public advisory with a PoC exists and EPSS assigns a high 36.9% probability of exploitation within 30 days (98th percentile).

What to do: Upgrade to Milvus 2.5.27 (2.5.x line) or 2.6.10 (2.6.x line). Until patched, restrict TCP port 9091 to trusted networks with firewall or security-group rules and do not expose the metrics/management port publicly; note that configuring a non-default etcd rootPath makes the /expr debug token less predictable. Check whether port 9091 is reachable from untrusted networks and review logs for unauthenticated requests to /api/v1/* or /expr.