Azure Cosmos DB ChaosDB Exposed Cross-Tenant Database Access

Wiz disclosed ChaosDB, a critical cross-tenant vulnerability chain in Azure Cosmos DB's Jupyter Notebook feature. Misconfigurations let notebook C# code execute as root, bypass container-local firewall controls, and reach Azure instance metadata and WireServer services on shared hosts. Researchers obtained certificates and private keys, authenticated to Azure Service Fabric, and decrypted Cosmos DB primary keys, notebook tokens, and storage-account credentials belonging to other customers. The exposed Cosmos DB keys enabled persistent full read, write, and delete access to affected accounts, and Wiz reported access to databases associated with several thousand Azure customers.

Microsoft disabled the vulnerable notebook service within 48 hours of the August 2021 report and later confirmed that several thousand customers were affected; it revoked some credentials and notified more than 30% of Cosmos DB customers to rotate keys. Organizations with Jupyter Notebooks enabled—especially accounts permitting external or cross-tenant network access—were advised to regenerate primary keys, restrict network exposure, move from shared keys to RBAC, and use private endpoints. Wiz later used ChaosDB to introduce PEACH, a tenant-isolation assessment framework covering Privilege, Encryption, Authentication, Connectivity, and Hygiene to identify and harden cross-tenant boundaries in cloud applications.