CVE-2026-106503: Backstage Scaffolder Action Input Authorization Bypass Vulnerability
HIGHCVE-2026-106503 is a HIGH (CVSS 8.1) scaffolder action input authorization bypass vulnerability (CWE-284: Improper Access Control) affecting Backstage libraries in the npm ecosystem. The issue involves scaffolder action input authorization bypass. Remediation is available by upgrading affected packages to version 3.3.1, 3.4.1, 4.0.3, 4.1.0.
CVE-2026-106503 at a Glance
Security Impact
CVSS: 8.1
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:H/I:H/A:N).
How to Fix CVE-2026-106503
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.
npm install @backstage/plugin-scaffolder-backend@3.3.1npm install @backstage/plugin-scaffolder-backend@3.4.1npm install @backstage/plugin-scaffolder-backend@4.0.3npm install @backstage/plugin-scaffolder-backend@4.1.0Run the following command in your project directory to verify that all resolved dependencies use the patched release:
npm ls @backstage/plugin-scaffolder-backendHow to Check if You Are Affected
To determine whether your Node.js application is affected by CVE-2026-106503, inspect your project dependencies using npm:
npm ls @backstage/plugin-scaffolder-backendAnalyze 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 3.3.1), your application is affected.
Note: The npm ls @backstage/plugin-scaffolder-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-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
CVE-2026-106503 Affected Backstage Versions
4 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
@backstage/plugin-scaffolder-backend
|
npm |
< 3.3.1
|
3.3.1
|
|
@backstage/plugin-scaffolder-backend
|
npm |
≥ 3.4.0
< 3.4.1
|
3.4.1
|
|
@backstage/plugin-scaffolder-backend
|
npm |
≥ 4.0.0
< 4.0.3
|
4.0.3
|
|
@backstage/plugin-scaffolder-backend
|
npm |
≥ 4.0.4
< 4.1.0
|
4.1.0
|
References
Frequently Asked Questions
What is CVE-2026-106503?
Which Backstage versions are affected?
What version fixes CVE-2026-106503?
Is @backstage/plugin-scaffolder-backend affected?
What is the CVSS score of CVE-2026-106503?
What CWE is associated with CVE-2026-106503?
How can I check npm dependencies for CVE-2026-106503?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-hmp2-4m7g-22cv",
"modified" : "2026-10-07T17:59:08Z",
"published" : "2026-10-07T17:59:08Z",
"aliases" : [ "CVE-2026-106503" ],
"summary" : "Backstage: Scaffolder action input authorization bypass",
"details" : "### Impact\n\nAn authenticated user with access to affected Scaffolder templates could bypass configured action restrictions. Depending on integration credentials, this could grant unauthorized access to repositories and related source-control resources.\n\n### Patches\n\nPatched in `@backstage/plugin-scaffolder-backend` version `4.1.0`\n\n### Workarounds\n\n- Restrict affected Scaffolder actions to trusted users and configure source-control integrations with least-privilege credentials.",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "npm",
"name" : "@backstage/plugin-scaffolder-backend"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "3.3.1"
} ]
} ]
}, {
"package" : {
"ecosystem" : "npm",
"name" : "@backstage/plugin-scaffolder-backend"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "3.4.0"
}, {
"fixed" : "3.4.1"
} ]
} ]
}, {
"package" : {
"ecosystem" : "npm",
"name" : "@backstage/plugin-scaffolder-backend"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "4.0.0"
}, {
"fixed" : "4.0.3"
} ]
} ]
}, {
"package" : {
"ecosystem" : "npm",
"name" : "@backstage/plugin-scaffolder-backend"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "4.0.4"
}, {
"fixed" : "4.1.0"
} ]
} ]
} ],
"references" : [ {
"type" : "WEB",
"url" : "https://github.com/backstage/backstage/security/advisories/GHSA-hmp2-4m7g-22cv"
}, {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-106503"
}, {
"type" : "WEB",
"url" : "https://github.com/backstage/backstage/commit/11c1384c0649b8ab26391c6a4e4f34b80ab0d188"
}, {
"type" : "WEB",
"url" : "https://github.com/backstage/backstage/commit/a91ed72d540e80b62a73b39bb1563ff5018d52d1"
}, {
"type" : "WEB",
"url" : "https://github.com/backstage/backstage/commit/e307e4f487103d815e484291b3fda778ab9983bf"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/backstage/backstage"
}, {
"type" : "WEB",
"url" : "https://github.com/backstage/backstage/releases/tag/v1.49.6"
}, {
"type" : "WEB",
"url" : "https://github.com/backstage/backstage/releases/tag/v1.50.5"
}, {
"type" : "WEB",
"url" : "https://github.com/backstage/backstage/releases/tag/v1.54.6"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-178", "CWE-284" ],
"severity" : "HIGH",
"github_reviewed" : true,
"github_reviewed_at" : "2026-10-07T17:59:08Z",
"nvd_published_at" : "2026-10-06T22:17:05Z"
}
}