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High, CVSS 8.0amended

Backstage Scaffolder plugin has insecure sandbox

CVE-2023-35926GHSA-wg6p-jmpc-xjmr

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (@backstage/plugin-scaffolder-backend 1.15.0), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
8.0 · CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H
EPSS
  • CVE-2023-35926: 1.89% estimated exploitation activity in the next 30 days; percentile 79.56 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

The Backstage scaffolder-backend plugin uses a templating library that requires a sandbox, as it by design allows for code injection. The library used for this sandbox so far has been vm2, but in light of several past vulnerabilities and existing vulnerabilities that may not have a fix, the plugin has switched to using a different sandbox library. Impact A malicious actor with write access to a registered scaffolder template could manipulate the template in a way that allows for remote code execution on the scaffolder-backend instance. This was only exploitable in the template YAML definition itself and not by user input data. Patches This is vulnerability is fixed in version 1.15.0 of @backstage/plugin-scaffolder-backend. Workarounds Note that the Backstage Threat Model states that scaffolder templates are considered to be a sensitive area that with the recommendation that you control access and perform manual reviews of changes to the scaffolder templates. The exploit is of a…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-wg6p-jmpc-xjmr

  2. Revision 1 · created ·

    Published from osv record GHSA-wg6p-jmpc-xjmr

Agent brief

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# Patch Next advisory brief: CVE-2023-35926

Advisory: Backstage Scaffolder plugin has insecure sandbox
IDs: CVE-2023-35926, GHSA-wg6p-jmpc-xjmr
Record: https://patchnext.com/advisories/cve-2023-35926 (revision 2, source checked 26 Oct 2026, 12:29 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @backstage/plugin-scaffolder-backend 1.15.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @backstage/plugin-scaffolder-backend: affected < 1.15.0; fixed in 1.15.0

## Suggested inspection (read-only)
- `npm ls @backstage/plugin-scaffolder-backend --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @backstage/plugin-scaffolder-backend.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-wg6p-jmpc-xjmr (OSV record GHSA-wg6p-jmpc-xjmr lists affected ranges: npm @backstage/plugin-scaffolder-backend >=0 <1.15.0 (fixed))
- Verified: https://github.com/advisories/GHSA-wg6p-jmpc-xjmr (GitHub-reviewed advisory GHSA-wg6p-jmpc-xjmr lists affected ranges: npm @backstage/plugin-scaffolder-backend >=0 <1.15.0)

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