CVE-2026-39961

Aiven Operator for Kubernetes versions 0.31.0 through 0.36.x contains a privilege escalation vulnerability affecting ClickhouseUser custom resource definitions. A developer with basic create permissions in their own namespace can exploit a "confused deputy" flaw in the operator's ServiceAccount to exfiltrate sensitive secrets from any other namespace, including production database credentials and API keys. The operator blindly trusts user-supplied namespace values without validation and lacks admission webhook enforcement, allowing unauthorized cross-namespace secret access. The vulnerability has a CVSS v3.1 score of 6.8 (MEDIUM) with a network-based attack vector, low complexity, and high-privilege requirement. Impact is limited to confidentiality loss with no integrity or availability impact. The attack requires administrator or developer-level permissions but can compromise critical production secrets cluster-wide, making it a significant insider threat concern. The vulnerability is not currently listed in the Known Exploited Vulnerabilities (KEV) catalog and shows minimal exploitation activity in the wild with an EPSS score of 0.0003. No public exploit code is widely available. The issue was fixed in version 0.37.0, and community attention remains low, suggesting limited active exploitation at this time. Organizations running affected versions should prioritize patching to prevent credential theft by compromised or malicious developers.