CVE-2026-106563: Backstage Improper Entity Validation Vulnerability

MODERATE
Advisory Identifier: GHSA-r9ph-3637-55px
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CVSS 5.3
CWE-20 CWE-862
Published
Advisory Summary

CVE-2026-106563 is a MODERATE (CVSS 5.3) improper entity validation vulnerability (CWE-20: Improper Input Validation) affecting Backstage libraries in the npm ecosystem. The issue involves improper entity validation in deprecated kubernetes services endpoint. Remediation is available by upgrading affected packages to version 0.21.8.

CVE-2026-106563 at a Glance

CVE Identifier CVE-2026-106563
GHSA Identifier GHSA-r9ph-3637-55px
Severity MODERATE
CVSS v3.1 Base Score 5.3
CWE Classification CWE-20: Improper Input Validation
Affected Product Backstage
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 5.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2026-106563

To remediate this vulnerability, upgrade all affected Backstage dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

@backstage/plugin-kubernetes-backend fixed: 0.21.8 
npm install @backstage/plugin-kubernetes-backend@0.21.8
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls @backstage/plugin-kubernetes-backend

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-106563, inspect your project dependencies using npm:

npm ls @backstage/plugin-kubernetes-backend

Analyze the terminal output to locate any version of Backstage in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.21.8), your application is affected.

Note: The npm ls @backstage/plugin-kubernetes-backend command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-20: Improper Input Validation, where the product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. In Backstage, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact An authenticated user with Kubernetes read permissions could access Kubernetes workload data beyond their intended scope by supplying crafted entity data to the deprecated services endpoint. The exposure is limited to read-only access to Kubernetes object metadata across configured clusters. ### Patches Patched in `@backstage/plugin-kubernetes-backend` version 0.21.8. ### Workarounds - Disable the deprecated `/services/:serviceId` route by deploying a custom Kubernetes router that omits it. - Restrict access to the `kubernetes.resources.read` permission to limit the set of users who can reach the endpoint.

CVE-2026-106563 Affected Backstage Versions

1 component(s)
Fixed Versions:
0.21.8
Product / Package Ecosystem Affected Versions Fixed Version
@backstage/plugin-kubernetes-backend
npm/@backstage/plugin-kubernetes-backend
npm
< 0.21.8
0.21.8

References

GitHub Advisory / Wiki ADVISORY
https://github.com/backstage/backstage/security/advisories/GHSA-r9ph-3637-55px
NVD — CVE-2026-106563 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-106563
Security Fix Commit FIX COMMIT
https://github.com/backstage/backstage/commit/2d5d3e77d630455d6d48cfa8f31fd3c126fd6f29
Backstage Source Repository REPOSITORY
https://github.com/backstage/backstage
Backstage Release RELEASE
https://github.com/backstage/backstage/releases/tag/v1.54.1

Frequently Asked Questions

What is CVE-2026-106563?
CVE-2026-106563 is a security vulnerability in Backstage involving Improper entity validation in deprecated Kubernetes services endpoint under CWE-20: Improper Input Validation.
Which Backstage versions are affected?
Affected versions include releases prior to 0.21.8 across affected packages: @backstage/plugin-kubernetes-backend.
What version fixes CVE-2026-106563?
Upgrading to 0.21.8 (or the latest patched release for your respective branch) resolves the vulnerability.
Is @backstage/plugin-kubernetes-backend affected?
Yes, @backstage/plugin-kubernetes-backend is affected in releases prior to 0.21.8. Upgrade your dependency to 0.21.8 or later.
What is the CVSS score of CVE-2026-106563?
CVE-2026-106563 has a CVSS v3.1 base score of 5.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N.
What CWE is associated with CVE-2026-106563?
CVE-2026-106563 is classified under CWE-20: Improper Input Validation (The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.).
How can I check npm dependencies for CVE-2026-106563?
Run the dependency tree command: 'npm ls @backstage/plugin-kubernetes-backend'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-r9ph-3637-55px",
  "modified" : "2026-10-07T18:02:37Z",
  "published" : "2026-10-07T18:02:37Z",
  "aliases" : [ "CVE-2026-106563" ],
  "summary" : "Backstage: Improper entity validation in deprecated Kubernetes services endpoint",
  "details" : "### Impact\n\nAn authenticated user with Kubernetes read permissions could access Kubernetes workload data beyond their intended scope by supplying crafted entity data to the deprecated services endpoint. The exposure is limited to read-only access to Kubernetes object metadata across configured clusters.\n\n### Patches\n\nPatched in `@backstage/plugin-kubernetes-backend` version 0.21.8.\n\n### Workarounds\n\n- Disable the deprecated `/services/:serviceId` route by deploying a custom Kubernetes router that omits it.\n- Restrict access to the `kubernetes.resources.read` permission to limit the set of users who can reach the endpoint.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@backstage/plugin-kubernetes-backend"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.21.8"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/backstage/backstage/security/advisories/GHSA-r9ph-3637-55px"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-106563"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/backstage/backstage/commit/2d5d3e77d630455d6d48cfa8f31fd3c126fd6f29"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/backstage/backstage"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/backstage/backstage/releases/tag/v1.54.1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20", "CWE-862" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-07T18:02:37Z",
    "nvd_published_at" : "2026-10-07T15:17:17Z"
  }
}