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7.1
External Secrets Operator: DNS-based Secret Leaks through Templates
GHSA-r2pg-r6h7-crf3
CVE-2026-34984
Summary
The External Secrets Operator's template engine can leak secrets to the internet if an attacker creates or updates a templated ExternalSecret resource. This can happen if the controller can perform DNS lookups and untrusted users can create or update resources. To protect your secrets, ensure that only trusted users can create or update ExternalSecret resources, and consider restricting DNS access for the controller.
What to do
- Update github.com external-secrets to version 1.3.3-0.20260331202714-6800989bdc12.
Affected software
| Vendor | Product | Affected versions | Fix available |
|---|---|---|---|
| github.com | external-secrets | <= 1.3.3-0.20260331202714-6800989bdc12 | 1.3.3-0.20260331202714-6800989bdc12 |
| github.com | external-secrets | > 2.0.0 , <= 2.2.0 | – |
Original title
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/templa...
Original description
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.
ghsa CVSS4.0
7.1
Vulnerability type
CWE-200
Information Exposure
Published: 14 Apr 2026 · Updated: 14 Apr 2026 · First seen: 13 Apr 2026