CVE-2026-106495: Backstage Improper Access Control Vulnerability

MODERATE
Advisory Identifier: GHSA-3xr5-8w6c-p5gw
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CVSS 4.3
CWE-284
Published
Advisory Summary

CVE-2026-106495 is a MODERATE (CVSS 4.3) improper access control vulnerability (CWE-284: Improper Access Control) affecting Backstage libraries in the npm ecosystem. The issue involves improper access control in backend action invocation. Remediation is available by upgrading affected packages to version 0.17.8.

CVE-2026-106495 at a Glance

CVE Identifier CVE-2026-106495
GHSA Identifier GHSA-3xr5-8w6c-p5gw
Severity MODERATE
CVSS v3.1 Base Score 4.3
CWE Classification CWE-284: Improper Access Control
Affected Product Backstage
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 4.3

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

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

How to Fix CVE-2026-106495

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/backend-defaults fixed: 0.17.8 
npm install @backstage/backend-defaults@0.17.8
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/backend-defaults

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-106495, inspect your project dependencies using npm:

npm ls @backstage/backend-defaults

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 0.17.8), your application is affected.

Note: The npm ls @backstage/backend-defaults 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-284: Improper Access Control, where the product does not restrict or incorrectly restricts access to a resource from an unauthorized 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 An authenticated user could invoke actions that an operator had excluded through action configuration. Existing action permissions and downstream authorization remain enforced. ### Patches Patched in `@backstage/backend-defaults` version `0.17.8` ### Workarounds Limit access to action invocation endpoints to trusted service callers until upgrading.

CVE-2026-106495 Affected Backstage Versions

1 component(s)
Fixed Versions:
0.17.8
Product / Package Ecosystem Affected Versions Fixed Version
@backstage/backend-defaults
npm/@backstage/backend-defaults
npm
< 0.17.8
0.17.8

References

GitHub Advisory / Wiki ADVISORY
https://github.com/backstage/backstage/security/advisories/GHSA-3xr5-8w6c-p5gw
NVD — CVE-2026-106495 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-106495
Security Fix Commit FIX COMMIT
https://github.com/backstage/backstage/commit/a8fb34a990a69bcb745e85a3213cf9e5ba2d31a3
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-2026-106495?
CVE-2026-106495 is a security vulnerability in Backstage involving Improper access control in backend action invocation under CWE-284: Improper Access Control.
Which Backstage versions are affected?
Affected versions include releases prior to 0.17.8 across affected packages: @backstage/backend-defaults.
What version fixes CVE-2026-106495?
Upgrading to 0.17.8 (or the latest patched release for your respective branch) resolves the vulnerability.
Is @backstage/backend-defaults affected?
Yes, @backstage/backend-defaults is affected in releases prior to 0.17.8. Upgrade your dependency to 0.17.8 or later.
What is the CVSS score of CVE-2026-106495?
CVE-2026-106495 has a CVSS v3.1 base score of 4.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N.
What CWE is associated with CVE-2026-106495?
CVE-2026-106495 is classified under CWE-284: Improper Access Control (The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.).
How can I check npm dependencies for CVE-2026-106495?
Run the dependency tree command: 'npm ls @backstage/backend-defaults'. 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-3xr5-8w6c-p5gw",
  "modified" : "2026-10-15T20:21:54Z",
  "published" : "2026-10-15T20:21:54Z",
  "aliases" : [ "CVE-2026-106495" ],
  "summary" : "Backstage: Improper access control in backend action invocation",
  "details" : "### Impact\n\nAn authenticated user could invoke actions that an operator had excluded through action configuration. Existing action permissions and downstream authorization remain enforced.\n\n### Patches\n\nPatched in `@backstage/backend-defaults` version `0.17.8`\n\n### Workarounds\n\nLimit access to action invocation endpoints to trusted service callers until upgrading.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@backstage/backend-defaults"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.17.8"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/backstage/backstage/security/advisories/GHSA-3xr5-8w6c-p5gw"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-106495"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/backstage/backstage/commit/a8fb34a990a69bcb745e85a3213cf9e5ba2d31a3"
  }, {
    "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-284" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-15T20:21:54Z",
    "nvd_published_at" : "2026-10-12T21:17:08Z"
  }
}