CVE-2026-106499: Backstage Secret-derived Values May Be Exposed Vulnerability

MODERATE
Advisory Identifier: GHSA-mfvq-x7vr-rgqg
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CVSS 4.9
CWE-532
Published
Advisory Summary

CVE-2026-106499 is a MODERATE (CVSS 4.9) secret-derived values may be exposed vulnerability (CWE-532: Insertion of Sensitive Information into Log File) affecting Backstage libraries in the npm ecosystem. The issue involves secret-derived values may be exposed in scaffolder task logs. Remediation is available by upgrading affected packages to version 4.1.0.

CVE-2026-106499 at a Glance

CVE Identifier CVE-2026-106499
GHSA Identifier GHSA-mfvq-x7vr-rgqg
Severity MODERATE
CVSS v3.1 Base Score 4.9
CWE Classification CWE-532: Insertion of Sensitive Information into Log File
Affected Product Backstage
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 4.9

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

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required High (PR:H)
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-2026-106499

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-scaffolder-backend fixed: 4.1.0 
npm install @backstage/plugin-scaffolder-backend@4.1.0
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-scaffolder-backend

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-106499, inspect your project dependencies using npm:

npm ls @backstage/plugin-scaffolder-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 4.1.0), 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-532: Insertion of Sensitive Information into Log File, where the product writes sensitive information to a log file. 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 that configure sensitive `scaffolder.defaultEnvironment.secrets` and allow an attacker to create or modify Scaffolder templates are affected. A template author could cause secret-derived values used during template iteration to be persisted in task logs, exposing those values to users with access to the resulting task logs. ### Patches Patched in `@backstage/plugin-scaffolder-backend` version `4.1.0` ### Workarounds - Restrict permission to create or update Template entities to fully trusted parties, as recommended by the Backstage threat model. - If that restriction cannot be guaranteed, remove sensitive values from `scaffolder.defaultEnvironment.secrets` until a patched version is available. No complete workaround is known that preserves both untrusted template authoring and access to sensitive default-environment secrets.

CVE-2026-106499 Affected Backstage Versions

1 component(s)
Fixed Versions:
4.1.0
Product / Package Ecosystem Affected Versions Fixed Version
@backstage/plugin-scaffolder-backend
npm/@backstage/plugin-scaffolder-backend
npm
< 4.1.0
4.1.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/backstage/backstage/security/advisories/GHSA-mfvq-x7vr-rgqg
NVD — CVE-2026-106499 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-106499
Security Fix Commit FIX COMMIT
https://github.com/backstage/backstage/commit/dc30fae2d96cb1606d36cc40b242f9b9e539bd70
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-2026-106499?
CVE-2026-106499 is a security vulnerability in Backstage involving Secret-derived values may be exposed in scaffolder task logs under CWE-532: Insertion of Sensitive Information into Log File.
Which Backstage versions are affected?
Affected versions include releases prior to 4.1.0 across affected packages: @backstage/plugin-scaffolder-backend.
What version fixes CVE-2026-106499?
Upgrading to 4.1.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is @backstage/plugin-scaffolder-backend affected?
Yes, @backstage/plugin-scaffolder-backend is affected in releases prior to 4.1.0. Upgrade your dependency to 4.1.0 or later.
What is the CVSS score of CVE-2026-106499?
CVE-2026-106499 has a CVSS v3.1 base score of 4.9 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N.
What CWE is associated with CVE-2026-106499?
CVE-2026-106499 is classified under CWE-532: Insertion of Sensitive Information into Log File (The product writes sensitive information to a log file.).
How can I check npm dependencies for CVE-2026-106499?
Run the dependency tree command: 'npm ls @backstage/plugin-scaffolder-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-mfvq-x7vr-rgqg",
  "modified" : "2026-10-07T17:59:14Z",
  "published" : "2026-10-07T17:59:14Z",
  "aliases" : [ "CVE-2026-106499" ],
  "summary" : "Backstage: Secret-derived values may be exposed in scaffolder task logs",
  "details" : "### Impact\n\nDeployments that configure sensitive `scaffolder.defaultEnvironment.secrets` and allow an attacker to create or modify Scaffolder templates are affected. A template author could cause secret-derived values used during template iteration to be persisted in task logs, exposing those values to users with access to the resulting task logs.\n\n### Patches\n\nPatched in `@backstage/plugin-scaffolder-backend` version `4.1.0`\n\n### Workarounds\n\n- Restrict permission to create or update Template entities to fully trusted parties, as recommended by the Backstage threat model.\n- If that restriction cannot be guaranteed, remove sensitive values from `scaffolder.defaultEnvironment.secrets` until a patched version is available.\n\nNo complete workaround is known that preserves both untrusted template authoring and access to sensitive default-environment secrets.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@backstage/plugin-scaffolder-backend"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.1.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/backstage/backstage/security/advisories/GHSA-mfvq-x7vr-rgqg"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-106499"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/backstage/backstage/commit/dc30fae2d96cb1606d36cc40b242f9b9e539bd70"
  }, {
    "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-532" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-07T17:59:14Z",
    "nvd_published_at" : "2026-10-06T22:17:04Z"
  }
}