CVE-2026-106563 backstage CVE debrief

Who should care

Defenders responsible for Kubernetes deployments using `@backstage/plugin-kubernetes-backend` should assess exposure and prioritize remediation. This includes operators, platform teams, vulnerability management teams, and security teams who need to verify exposure and restrict access to the deprecated endpoint.

Why it matters

CVE-2026-106563 is a vulnerability in `@backstage/plugin-kubernetes-backend` that allows authenticated users with Kubernetes read permissions to access Kubernetes workload data beyond their intended scope. Defenders should prioritize verifying exposure and restricting access to the deprecated endpoint.

• Read-only access to Kubernetes object metadata across configured clusters for authenticated users with Kubernetes read permissions may be possible.
• Verification of exposure in Kubernetes deployments is necessary.
• Restricting access to the deprecated endpoint can limit the attack surface.
• Updating to version 0.21.8 or later can mitigate the vulnerability.

Technical summary

The `@backstage/plugin-kubernetes-backend` package has a vulnerability in the deprecated Kubernetes services endpoint. An authenticated user with Kubernetes read permissions could access Kubernetes workload data beyond their intended scope by supplying crafted entity data. The exposure is limited to read-only access to Kubernetes object metadata across configured clusters. Defenders should prioritize verifying exposure in their Kubernetes deployments, especially where `@backstage/plugin-kubernetes-backend` is used, and restrict access to the deprecated `/services/:serviceId` route.

Defensive priority

Defenders should prioritize verifying exposure in their Kubernetes deployments, especially where `@backstage/plugin-kubernetes-backend` is used, and restrict access to the deprecated `/services/:serviceId` route.

Recommended defensive actions

• Verify if `@backstage/plugin-kubernetes-backend` is used in your environment and assess exposure.
• Restrict access to the `kubernetes.resources.read` permission to limit the set of users who can reach the deprecated endpoint.
• Consider disabling the deprecated `/services/:serviceId` route by deploying a custom Kubernetes router that omits it.
• Update `@backstage/plugin-kubernetes-backend` to version 0.21.8 or later.
• Review compensating controls for exposed systems while remediation is scheduled and verified.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.

Evidence notes

The CVE record and source item provide details on the vulnerability in `@backstage/plugin-kubernetes-backend`. The exposure is limited to read-only access to Kubernetes object metadata across configured clusters for authenticated users with Kubernetes read permissions.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.