Kroxylicious-kms-provider-azure-key-vault-kms: streams for apache kafka kroxylicious: azure key vault ssrf exfiltrates bearer token via untrusted edek vaultname

Overview

The Azure Key Vault KMS provider in Kroxylicious accepts an untrusted vaultName from wire-deserialized EDEK bytes without format validation, enabling SSRF that exfiltrates the proxy's Azure bearer token to an attacker-controlled host. Token replay against the real Key Vault defeats the entire record-encryption trust model.

Affected

• kroxylicious-kms-provider-azure-key-vault-kms (all versions)

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Workarounds

1. Restrict outbound network access — use Kubernetes NetworkPolicy to limit proxy pod egress to only legitimate Azure Key Vault endpoints on port 443.
2. Monitor KMS call patterns — alert on unwrap requests targeting unexpected vault hostnames.

--- CME Mitigation Guidance (2026-10-20) --- Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure.

The highest-value action is to enforce strict allowlist regex validation on wire-deserialized vaultName in the Azure Key Vault KMS provider before constructing outbound HTTP endpoints: upgrade to kroxylicious-kms-provider-azure-key-vault-kms 0.25.1+ (or the fixed Kroxylicious Kms Provider Azure Key Vault Kms builds), which validate Key Vault name using validateKeyVaultName to reject names containing dots, URL fragments, invalid lengths, or malformed hyphens before constructing the Key Vault URL, closing all 2 injection vectors (crafted EDEK containing an arbitrary hostname in vaultName, vaultName URL fragment injection). Until patched, this is a concern on Kafka clusters using the Kroxylicious Record Encryption filter with Azure Key Vault KMS, so restrict proxy pod outbound network egress using Kubernetes NetworkPolicy strictly to legitimate Azure Key Vault endpoints on port 443 and alert on unwrap requests targeting unexpected vault hostnames. As a compensating measure, Deploy Falco or eBPF runtime security to detect anomalous outbound network connections initiated by the Kroxylicious proxy process to unexpected destinations. These controls limit blast radius and contain exploitation, but they do not fix the underlying unvalidated input SSRF defect — apply the upstream patch to fully remediate.

Highest-impact CME: CME-1315 Allowlist-Preferred Input Validation (Deny-by-Default Filtering) (high)