Kroxylicious Azure Key Vault KMS provider SSRF (CVE-2026-105941)

CVE-2026-105941 describes a critical security vulnerability within the Azure Key Vault KMS provider for Kroxylicious. The issue arises from a failure to perform adequate format validation on the vaultName field when handling wire-deserialized Encrypted Data Encryption Key (EDEK) bytes. By providing a crafted vaultName during the deserialization process, an unauthenticated attacker can force the application to perform a Server-Side Request Forgery (SSRF) request.

This request is directed toward an attacker-controlled endpoint, effectively exfiltrating the Azure bearer token assigned to the proxy service. Once obtained, the attacker can replay this bearer token against the legitimate Azure Key Vault service. This compromise allows the attacker to bypass the record-encryption trust model, potentially leading to unauthorized access to sensitive data encrypted by the proxy. Given the reliance of the proxy on this token for cryptographic operations, the impact on the confidentiality of the processed data is significant.

Impact

The vulnerability allows for the exfiltration of sensitive Azure identity tokens used by the Kroxylicious proxy. Successful exploitation results in the compromise of the record-encryption trust model, potentially enabling unauthorized decryption of data handled by the proxy. This impacts any environment using the Kroxylicious Azure Key Vault KMS provider, potentially affecting all organizations managing Kafka record encryption via this service.

Recommendation

• Monitor network traffic originating from the Kroxylicious service host for unauthorized egress connections to unknown or unexpected external hosts, particularly those attempting to communicate with Azure Identity endpoints.
• Identify and update all instances of the Kroxylicious Azure Key Vault KMS provider to the vendor-patched version immediately to remediate CVE-2026-105941.
• Review Azure Identity logs for signs of anomalous token usage or logins originating from unexpected IP addresses that correlate with potential replayed bearer tokens.