CVE-2026-106504 backstage CVE debrief

Who should care

Defenders responsible for Backstage deployments using `@backstage/plugin-scaffolder-backend` versions before 4.1.0 should assess exposure and prioritize verification and remediation efforts.

Why it matters

CVE-2026-106504 is a sensitive information exposure vulnerability in Backstage deployments using `@backstage/plugin-scaffolder-backend` versions before 4.1.0. An authenticated user who can create and read scaffolder tasks may observe sensitive values in task logs. Defenders should prioritize verifying exposure and restrict scaffolder task creation and task-log reading to trusted users.

• Verify exposure in Backstage deployments using `@backstage/plugin-scaffolder-backend` versions before 4.1.0.
• Restrict scaffolder task creation and task-log reading to trusted users.
• Avoid placing centrally managed sensitive values in inputs to actions that may be denied until upgrading.

Technical summary

An authenticated user who can create and read scaffolder tasks may be able to observe sensitive values in task logs in deployments with restrictive action permissions and affected templates. Exploitation requires a denied action whose input contains such a value. The vulnerability is patched in `@backstage/plugin-scaffolder-backend` version `4.1.0`. Defenders should prioritize verifying exposure in Backstage deployments using `@backstage/plugin-scaffolder-backend` versions before 4.1.0 and restrict scaffolder task creation and task-log reading to trusted users. Additionally, defenders should avoid placing centrally managed sensitive values in inputs to actions that may be denied until upgrading.

Defensive priority

Defenders should prioritize verifying exposure in Backstage deployments using `@backstage/plugin-scaffolder-backend` versions before 4.1.0 and restrict scaffolder task creation and task-log reading to trusted users.

Recommended defensive actions

• Verify if the `@backstage/plugin-scaffolder-backend` version is before 4.1.0 and upgrade to 4.1.0 or later if necessary.
• Restrict scaffolder task creation and task-log reading to trusted users.
• Avoid placing centrally managed sensitive values in inputs to actions that may be denied until upgrading.
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance.
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed.
• 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 source corpus provides details on the sensitive information exposure in scaffolder task logs in Backstage deployments with restrictive action permissions and affected templates. It mentions that exploitation requires a denied action whose input contains such a value.

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.