external-secrets up to 2.2.x DNS Resolution template.go TxtFuncMap information disclosure

Summaryinfo

A vulnerability marked as problematic has been reported in external-secrets up to 2.2.x. Affected is the function TxtFuncMap of the file runtime/template/v2/template.go of the component DNS Resolution Handler. This manipulation causes information disclosure. This vulnerability is registered as CVE-2026-34984. Remote exploitation of the attack is possible. No exploit is available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in external-secrets up to 2.2.x. It has been declared as problematic. Affected by this vulnerability is the function TxtFuncMap of the file runtime/template/v2/template.go of the component DNS Resolution Handler. The manipulation with an unknown input leads to a information disclosure vulnerability. The CWE definition for the vulnerability is CWE-200. The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. As an impact it is known to affect confidentiality. The summary by CVE is:

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.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-34984 since 03/31/2026. The exploitation appears to be easy. The attack can be launched remotely. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1592 according to MITRE ATT&CK.

Upgrading to version 2.3.0 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch 6800989bdc12782ca2605d3b8bf7f2876a16551a is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Name

• external-secrets

Version

• 2.0
• 2.1
• 2.2

License

• open-source

Website

• Product: https://github.com/external-secrets/external-secrets/

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