CVE-2026-106501: Backstage Scaffolder Information Disclosure

CVE-2026-106501 Overview

Backstage is an open framework for building developer portals maintained by the Cloud Native Computing Foundation. The @backstage/plugin-scaffolder-backend package exposes sensitive internal task execution data to authenticated users who can read another user's Scaffolder task. When that data contains credentials for external services, attackers can retrieve those secrets and perform unauthorized actions in connected systems. The issue is classified under CWE-200: Exposure of Sensitive Information to an Unauthorized Actor and is fixed in versions 3.3.1, 3.4.1, 4.0.3, and 4.1.0.

Critical Impact
Authenticated Backstage users can harvest credentials embedded in Scaffolder task state and secrets, enabling lateral movement into external services integrated with the developer portal.

Affected Products

Backstage @backstage/plugin-scaffolder-backend prior to 3.3.1
Backstage @backstage/plugin-scaffolder-backend prior to 3.4.1
Backstage @backstage/plugin-scaffolder-backend prior to 4.0.3 and 4.1.0

Discovery Timeline

2026-10-06 - CVE-2026-106501 published to NVD
2026-10-07 - Last updated in NVD database

Technical Details for CVE-2026-106501

Vulnerability Analysis

The Backstage Scaffolder plugin orchestrates software templates and tracks their execution as tasks stored in the backend database. Each task carries metadata including status, specification, state, and injected secrets used during template execution. The Scaffolder task API returned the full serialized task object, including the secrets and state fields, without filtering sensitive content before delivering it to the requesting user.

Any authenticated Backstage user with permission to read another user's task could retrieve credentials or tokens that the task used to interact with external services such as source code hosts, cloud providers, or package registries. Because these credentials often grant write access, the exposure permits unauthorized changes well beyond the Backstage instance itself.

Root Cause

The root cause is implicit serialization of the full task object through the auto-generated OpenAPI router. The SerializedTask model referenced TaskSecrets and the raw JsonObject state, so the HTTP response contained execution secrets alongside benign task metadata. There was no allow-list of fields to serialize for read operations.

Attack Vector

An authenticated attacker with a valid Backstage session queries the Scaffolder task endpoint for another user's task identifier. The response contains the secrets object and internal state, which commonly includes short-lived tokens, personal access tokens, cloud API keys, or service account credentials injected by templates at runtime.

typescript

// Patch: plugins/scaffolder-backend/src/schema/openapi/generated/models/SerializedTask.model.ts
// ******************************************************************
// * THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY. *
// ******************************************************************
-import { TaskSecrets } from '../models/TaskSecrets.model';
 import { TaskStatus } from '../models/TaskStatus.model';

typescript

// Patch: plugins/scaffolder-backend/src/schema/openapi/generated/router.ts
          createdBy: {
            type: 'string',
          },
-          secrets: {
-            $ref: '#/components/schemas/TaskSecrets',
-          },
-          state: {
-            $ref: '#/components/schemas/JsonObject',
-          },
        },
        required: ['id', 'spec', 'status', 'createdAt'],
        description: 'SerializedTask',

Source: Backstage Commit 66d2219. The fix removes secrets and state from the serialized task schema so the API no longer emits them in task read responses.

Detection Methods for CVE-2026-106501

Indicators of Compromise

Unusual read requests against Scaffolder task endpoints such as /api/scaffolder/v2/tasks/{taskId} originating from user accounts that did not create the task.
Spikes in task enumeration patterns where a single authenticated principal retrieves many task identifiers in a short window.
Use of credentials obtained from Scaffolder tasks against external services from IP addresses or user agents inconsistent with the original template execution context.

Detection Strategies

Correlate Backstage audit logs with external service authentication events to identify tokens being replayed by principals other than the task owner.
Inspect reverse proxy or ingress logs for response bodies containing the secrets field on Scaffolder task routes prior to patching.
Baseline per-user Scaffolder task read volume and alert on deviations that suggest harvesting.

Monitoring Recommendations

Forward Backstage backend logs and external service audit trails to a centralized SIEM for cross-source correlation.
Enable short credential lifetimes and rotation events as detection signals when tokens are used after a task completes.
Track GitHub, GitLab, cloud provider, and package registry API calls for anomalous activity tied to service accounts that Scaffolder templates use.

How to Mitigate CVE-2026-106501

Immediate Actions Required

Upgrade @backstage/plugin-scaffolder-backend to 3.3.1, 3.4.1, 4.0.3, or 4.1.0 depending on the Backstage release line in use.
Rotate every credential, token, and API key that any Scaffolder template has handled since the vulnerable version was deployed.
Audit Backstage access logs for prior Scaffolder task read activity by principals other than the task owner.

Patch Information

The maintainers released fixes aligned with Backstage releases v1.49.6, v1.50.5, and v1.54.6. The code changes are documented in Backstage Commit 66d2219, Backstage Commit c198388, and Backstage Commit e262d64. Full details are in the GitHub Security Advisory GHSA-g2v8-7jhw-pp8p.

Workarounds

Restrict Scaffolder task read permissions to the task owner using Backstage permission policies until patches are applied.
Prefer short-lived, scoped credentials in Scaffolder templates to reduce blast radius if secrets are exposed.
Place an API gateway or reverse proxy in front of Backstage that strips secrets and state fields from Scaffolder task responses as a temporary control.

bash

# Upgrade the vulnerable package to a fixed version
yarn up @backstage/plugin-scaffolder-backend@^4.1.0
# or, for the 4.0.x line
yarn up @backstage/plugin-scaffolder-backend@^4.0.3
# or, for the 3.4.x line
yarn up @backstage/plugin-scaffolder-backend@^3.4.1
# or, for the 3.3.x line
yarn up @backstage/plugin-scaffolder-backend@^3.3.1