CVE-2026-106559: Backstage Improper Input Validation Vulnerability

MODERATE
Advisory Identifier: GHSA-75qf-886x-5xf2
Share
CVSS 6.3
CWE-73 CWE-22
Published
Advisory Summary

CVE-2026-106559 is a MODERATE (CVSS 6.3) improper input validation vulnerability (CWE-73: External Control of File Name or Path) affecting Backstage libraries in the npm ecosystem. The issue involves improper input validation in confluence to markdown scaffolder module. Remediation is available by upgrading affected packages to version 0.3.25.

CVE-2026-106559 at a Glance

CVE Identifier CVE-2026-106559
GHSA Identifier GHSA-75qf-886x-5xf2
Severity MODERATE
CVSS v3.1 Base Score 6.3
CWE Classification CWE-73: External Control of File Name or Path
Affected Product Backstage
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 6.3

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:R/S:U/C:N/I:H/A:L).

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

How to Fix CVE-2026-106559

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-module-confluence-to-markdown fixed: 0.3.25 
npm install @backstage/plugin-scaffolder-backend-module-confluence-to-markdown@0.3.25
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-module-confluence-to-markdown

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-106559, inspect your project dependencies using npm:

npm ls @backstage/plugin-scaffolder-backend-module-confluence-to-markdown

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 0.3.25), your application is affected.

Note: The npm ls @backstage/plugin-scaffolder-backend-module-confluence-to-markdown 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-73: External Control of File Name or Path, where the product allows user input to control or influence paths or file names that are used in filesystem operations. 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 Insufficient input validation in the Confluence to Markdown scaffolder module could allow an attacker to influence file write operations during template execution. Exploitation requires a Backstage user to run a template that processes attacker-influenced Confluence content. ### Patches Patched in `@backstage/plugin-scaffolder-backend-module-confluence-to-markdown` version `0.3.25` ### Workarounds If unable to update immediately: - Restrict Confluence edit access to trusted users. - Review Confluence page content before running scaffolder templates against untrusted pages.

CVE-2026-106559 Affected Backstage Versions

1 component(s)
Fixed Versions:
0.3.25
Product / Package Ecosystem Affected Versions Fixed Version
@backstage/plugin-scaffolder-backend-module-confluence-to-markdown
npm/@backstage/plugin-scaffolder-backend-module-confluence-to-markdown
npm
< 0.3.25
0.3.25

References

GitHub Advisory / Wiki ADVISORY
https://github.com/backstage/backstage/security/advisories/GHSA-75qf-886x-5xf2
NVD — CVE-2026-106559 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-106559
Security Fix Commit FIX COMMIT
https://github.com/backstage/backstage/commit/506c2c11bce3ed9d1f8f50de5d6474b16e43a65e
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-2026-106559?
CVE-2026-106559 is a security vulnerability in Backstage involving Improper input validation in Confluence to Markdown scaffolder module under CWE-73: External Control of File Name or Path.
Which Backstage versions are affected?
Affected versions include releases prior to 0.3.25 across affected packages: @backstage/plugin-scaffolder-backend-module-confluence-to-markdown.
What version fixes CVE-2026-106559?
Upgrading to 0.3.25 (or the latest patched release for your respective branch) resolves the vulnerability.
Is @backstage/plugin-scaffolder-backend-module-confluence-to-markdown affected?
Yes, @backstage/plugin-scaffolder-backend-module-confluence-to-markdown is affected in releases prior to 0.3.25. Upgrade your dependency to 0.3.25 or later.
What is the CVSS score of CVE-2026-106559?
CVE-2026-106559 has a CVSS v3.1 base score of 6.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:H/A:L.
What CWE is associated with CVE-2026-106559?
CVE-2026-106559 is classified under CWE-73: External Control of File Name or Path (The product allows user input to control or influence paths or file names that are used in filesystem operations.).
How can I check npm dependencies for CVE-2026-106559?
Run the dependency tree command: 'npm ls @backstage/plugin-scaffolder-backend-module-confluence-to-markdown'. 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-75qf-886x-5xf2",
  "modified" : "2026-10-07T18:03:06Z",
  "published" : "2026-10-07T18:03:06Z",
  "aliases" : [ "CVE-2026-106559" ],
  "summary" : "Backstage: Improper input validation in Confluence to Markdown scaffolder module",
  "details" : "### Impact\n\nInsufficient input validation in the Confluence to Markdown scaffolder module could allow an attacker to influence file write operations during template execution. Exploitation requires a Backstage user to run a template that processes attacker-influenced Confluence content.\n\n### Patches\n\nPatched in `@backstage/plugin-scaffolder-backend-module-confluence-to-markdown` version `0.3.25`\n\n### Workarounds\n\nIf unable to update immediately:\n\n- Restrict Confluence edit access to trusted users.\n- Review Confluence page content before running scaffolder templates against untrusted pages.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:H/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@backstage/plugin-scaffolder-backend-module-confluence-to-markdown"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.3.25"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/backstage/backstage/security/advisories/GHSA-75qf-886x-5xf2"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-106559"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/backstage/backstage/commit/506c2c11bce3ed9d1f8f50de5d6474b16e43a65e"
  }, {
    "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-22", "CWE-73" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-07T18:03:06Z",
    "nvd_published_at" : "2026-10-07T15:17:17Z"
  }
}