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.

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-r2pg-r6h7-crf3 External Secrets Operator has DNS-based secret exfiltration via getHostByName in External Secrets v2 template engine
Fixes

Solution

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Workaround

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History

Tue, 14 Apr 2026 02:45:00 +0000

Type Values Removed Values Added
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.
Title External Secrets Operator has DNS exfiltration via getHostByName in its v2 template engine
Weaknesses CWE-200
References
Metrics cvssV4_0

{'score': 7.1, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-04-14T01:48:41.166Z

Reserved: 2026-03-31T19:38:31.617Z

Link: CVE-2026-34984

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-04-14T03:16:08.530

Modified: 2026-04-14T03:16:08.530

Link: CVE-2026-34984

cve-icon Redhat

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cve-icon OpenCVE Enrichment

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Weaknesses