CVE-2026-42876

ExternalSecrets allows users to craft Service Account tokens for misconfigured Service Accounts in namespaces the users have access to.

Workarounds

• Add admission control logic to prevent the use of Templates targeting undesired Types
• Remove Service Account Token generation via kube-controller-manager flags
• Restrict User RBAC on production clusters and sensitive namespaces

A user who only has permission to create ExternalSecret resources can cause the operator to create a Secret that Kubernetes will automatically populate with a long-lived token for the sepcified service account. This effectively allows the user to impersonate any service account in the namespace without needing direct create permissions on TokenRequest or Secrets of that type.

The problem is mitigated in severity by the fact that the user must have pre-existing permissions already at almost the same level as the escalation later gives. The attacker cannot use this method to gain access to more information without other things also being misconfigured in the ESO installation.

CVE-2026-42876 has a CVSS score of 4.9 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.4.1); upgrading removes the vulnerable code path.

Kodem intelligence

Disallow this combination including the bootstrap token secret type.

1. What is CVE-2026-42876? CVE-2026-42876 is a medium-severity security vulnerability in github.com/external-secrets/external-secrets/apis (go), affecting versions >= 0.1.0, < 2.4.1. It is fixed in 2.4.1.
2. How severe is CVE-2026-42876? CVE-2026-42876 has a CVSS score of 4.9 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/external-secrets/external-secrets/apis are affected by CVE-2026-42876? github.com/external-secrets/external-secrets/apis (go) versions >= 0.1.0, < 2.4.1 is affected.
4. Is there a fix for CVE-2026-42876? Yes. CVE-2026-42876 is fixed in 2.4.1. Upgrade to this version or later.
5. Is CVE-2026-42876 exploitable, and should I be worried? Whether CVE-2026-42876 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-42876 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-42876? Upgrade github.com/external-secrets/external-secrets/apis to 2.4.1 or later.