External Secrets Operator has DNS exfiltration via getHostByName in its v2 template engine

Summary

External Secrets Operator reads information from a third-party service and automatically injects the values as Kubernetes Secrets. Versions 2.2.0 and below contain a vulnerability in runtime/template/v2/template.go where the v2 template engine removes env and expandenv from Sprig's TxtFuncMap() but leaves the getHostByName function accessible to user-controlled templates. Since ESO executes templates within the controller process, an attacker who can create or update templated ExternalSecret resources can invoke controller-side DNS lookups using secret-derived values. This creates a DNS exfiltration primitive, allowing fetched secret material to be leaked via DNS queries without requiring direct outbound network access from the attacker's workload. The impact is a confidentiality issue, particularly in environments where untrusted or lower-trust users can author templated ExternalSecret resources and the controller has DNS resolution capability. This issue has been fixed in version 2.3.0.

Timeline

1. Apr 14, 2026, 1:48 AM UTCCVE published
2. Apr 14, 2026, 3:37 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Apr 14, 2026, 4:27 PM UTCRecord last updated

Affected versions

• external-secrets external-secrets

  fixed in 2.3.0

• github.com/external-secrets/external-secretsGo

  fixed in 1.3.3-0.20260331202714-6800989bdc12

• github.com/external-secrets/external-secretsGo

  From 2.0.0 · through 2.2.0

References 3