CVE-2026-42876 is a medium-severity (CVSS 4.9) CWE-285 vulnerability in github.com/external-secrets/external-secrets/apis. A fix is available for github.com/external-secrets/external-secrets/apis — see the affected versions and patch details below.
External Secrets Operator: Priviledge escalation with secret overwriting
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42876.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-42876 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/external-secrets/external-secrets/apisReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
ExternalSecrets allows users to craft Service Account tokens for misconfigured Service Accounts in namespaces the users have access to.
Impact
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.
Patches
Disallow this combination including the bootstrap token secret type.
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
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/external-secrets/external-secrets/apis | ≥ 0.1.0&&< 2.4.1 | 2.4.1go get github.com/external-secrets/external-secrets/apis@v2.4.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/external-secrets/external-secrets/apis, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/external-secrets/external-secrets/apis to 2.4.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42876 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-42876 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-42876. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-42876 in your dependencies?
O3 Security finds CVE-2026-42876 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.