External Secrets Operator's Missing Namespace Restriction Allows Unauthorized Secret Access

Summary

A vulnerability was discovered in the External Secrets Operator where the List() calls for Kubernetes Secret and SecretStore resources performed by the PushSecret controller did not apply a namespace selector.
This flaw allowed an attacker to use label selectors to list and read secrets/secret-stores across the cluster, bypassing intended namespace restrictions.

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Impact

An attacker with the ability to create or update PushSecret resources and control SecretStore configurations could exploit this vulnerability to exfiltrate sensitive data from arbitrary namespaces.
This could lead to full disclosure of Kubernetes secrets, including credentials, tokens, and other sensitive information stored in the cluster.

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Exploitability

To exploit this vulnerability, an attacker must:

1. Have permissions to create or update PushSecret resources.
2. Control one or more SecretStore resources.

With these conditions met, the attacker could leverage label selectors to list secrets from any namespace and retrieve their contents.

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Affected Versions

• Vulnerable: v0.15.0 – v0.19.1
• Not Vulnerable: v0.19.2 and later

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Fix

The vulnerability was addressed in v0.19.2 by adding namespace restrictions to the List() calls for both PushSecret and SecretStore controllers.
This ensures that only secrets in the intended namespace are accessible.

Relevant fixes:

• #5133 – Enforce namespace selector for PushSecret List() calls
• #5109 – Enforce namespace selector for SecretStore List() calls

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Mitigation

If upgrading to v0.19.2 or later is not immediately possible, the following mitigations are recommended:

• Restrict RBAC permissions so that only trusted service accounts can create or update PushSecret and SecretStore resources.
• Audit existing PushSecret and SecretStore resources to ensure they are controlled by trusted parties.
• Review Network Policies to prevent data exfiltration

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Credit

This vulnerability was reported by @gracedo and @moolen