CVE-2026-106487: Backstage Unsupported Catalog Cluster Authentication Mode Vulnerability

LOW
Advisory Identifier: GHSA-h53x-hjx6-25gr
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CVSS 3.5
CWE-441
Published
Advisory Summary

CVE-2026-106487 is a LOW (CVSS 3.5) unsupported catalog cluster authentication mode vulnerability (CWE-441: Unintended Proxy or Intermediary ('Confused Deputy')) affecting Backstage libraries in the npm ecosystem. The issue involves unsupported catalog cluster authentication mode in kubernetes backend. Remediation is available by upgrading affected packages to version 0.21.10.

CVE-2026-106487 at a Glance

CVE Identifier CVE-2026-106487
GHSA Identifier GHSA-h53x-hjx6-25gr
Severity LOW
CVSS v3.1 Base Score 3.5
CWE Classification CWE-441: Unintended Proxy or Intermediary ('Confused Deputy')
Affected Product Backstage
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 3.5

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:C/C:L/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 Changed (S:C)
Confidentiality Low (C:L)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2026-106487

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: 0.21.10 
npm install @backstage/plugin-kubernetes-backend@0.21.10
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-2026-106487, 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 0.21.10), 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-441: Unintended Proxy or Intermediary ('Confused Deputy'), where the product receives a request, message, or directive from an upstream component, but the product does not sufficiently preserve the original source of the request before forwarding the request to an external actor that is outside of the product's control sphere. this causes the product to appear to be the source of the request, leading it to act as a proxy or other intermediary between the upstream component and the external actor. 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 Deployments using catalog cluster discovery may be affected when catalog contributors can create or modify `kubernetes-cluster` Resource entities. With the required endpoint permissions and pod RBAC, the backend can use its local in-cluster identity, potentially exposing Kubernetes resources readable by that identity. The credential is used only with the local in-cluster API endpoint and is not sent to the catalog-supplied endpoint. ### Patches Patched in `@backstage/plugin-kubernetes-backend` version `0.21.10` ### Workarounds - Do not configure service account authentication through catalog-provided clusters; use the supported static configuration method when service account authentication is required. - Restrict catalog ingestion so untrusted users cannot create or alter Kubernetes cluster Resource entities.

CVE-2026-106487 Affected Backstage Versions

1 component(s)
Fixed Versions:
0.21.10
Product / Package Ecosystem Affected Versions Fixed Version
@backstage/plugin-kubernetes-backend
npm/@backstage/plugin-kubernetes-backend
npm
< 0.21.10
0.21.10

References

GitHub Advisory / Wiki ADVISORY
https://github.com/backstage/backstage/security/advisories/GHSA-h53x-hjx6-25gr
NVD — CVE-2026-106487 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-106487
Security Fix Commit FIX COMMIT
https://github.com/backstage/backstage/commit/c14f8be6908f0f719b16356e5492352311e28946
Backstage Source Repository REPOSITORY
https://github.com/backstage/backstage
Backstage Release RELEASE
https://github.com/backstage/backstage/releases/tag/v1.54.6

Frequently Asked Questions

What is CVE-2026-106487?
CVE-2026-106487 is a security vulnerability in Backstage involving Unsupported catalog cluster authentication mode in kubernetes backend under CWE-441: Unintended Proxy or Intermediary ('Confused Deputy').
Which Backstage versions are affected?
Affected versions include releases prior to 0.21.10 across affected packages: @backstage/plugin-kubernetes-backend.
What version fixes CVE-2026-106487?
Upgrading to 0.21.10 (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 0.21.10. Upgrade your dependency to 0.21.10 or later.
What is the CVSS score of CVE-2026-106487?
CVE-2026-106487 has a CVSS v3.1 base score of 3.5 (LOW) with vector string CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:N/A:N.
What CWE is associated with CVE-2026-106487?
CVE-2026-106487 is classified under CWE-441: Unintended Proxy or Intermediary ('Confused Deputy') (The product receives a request, message, or directive from an upstream component, but the product does not sufficiently preserve the original source of the request before forwarding the request to an external actor that is outside of the product's control sphere. This causes the product to appear to be the source of the request, leading it to act as a proxy or other intermediary between the upstream component and the external actor.).
How can I check npm dependencies for CVE-2026-106487?
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-h53x-hjx6-25gr",
  "modified" : "2026-10-07T18:01:08Z",
  "published" : "2026-10-07T18:01:08Z",
  "aliases" : [ "CVE-2026-106487" ],
  "summary" : "Backstage: Unsupported catalog cluster authentication mode in kubernetes backend",
  "details" : "### Impact\n\nDeployments using catalog cluster discovery may be affected when catalog contributors can create or modify `kubernetes-cluster` Resource entities. With the required endpoint permissions and pod RBAC, the backend can use its local in-cluster identity, potentially exposing Kubernetes resources readable by that identity. The credential is used only with the local in-cluster API endpoint and is not sent to the catalog-supplied endpoint.\n\n### Patches\n\nPatched in `@backstage/plugin-kubernetes-backend` version `0.21.10`\n\n### Workarounds\n\n- Do not configure service account authentication through catalog-provided clusters; use the supported static configuration method when service account authentication is required.\n- Restrict catalog ingestion so untrusted users cannot create or alter Kubernetes cluster Resource entities.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@backstage/plugin-kubernetes-backend"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.21.10"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/backstage/backstage/security/advisories/GHSA-h53x-hjx6-25gr"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-106487"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/backstage/backstage/commit/c14f8be6908f0f719b16356e5492352311e28946"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/backstage/backstage"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/backstage/backstage/releases/tag/v1.54.6"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-441" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-07T18:01:08Z",
    "nvd_published_at" : "2026-10-06T21:17:17Z"
  }
}