Maker.js has Unsafe Property Copying in makerjs.extendObject

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

EPSS

• CVE-2026-24888: 1.00% estimated exploitation activity in the next 30 days; percentile 62.77 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The makerjs.extendObject function copies properties from source objects without proper validation, potentially exposing applications to security risks. The function lacks hasOwnProperty() checks and does not filter dangerous keys, allowing inherited properties and potentially malicious properties to be copied to target objects. Details The extendObject function iterates over source object properties using a for...in loop without: 1. Checking hasOwnProperty() to exclude inherited properties 2. Filtering dangerous keys (proto, constructor, prototype) 3. Validating property sources Affected Code File: https://github.com/microsoft/maker.js/blob/98cffa82a372ff942194c925a12a311253587167/packages/maker.js/src/core/maker.ts#L232-L241 PoC Impact Security Implications 1. Unexpected Behavior: Properties may appear on target objects but not be own properties, breaking hasOwnProperty() assumptions in security-sensitive code. 2. Security Bypass Risk: Code relying on hasOwnProperty() for…

Published by the source

29 Jan 2026, 15:18 UTC

Last modified by the source

3 Feb 2026, 03:03 UTC

Source last checked

26 Oct 2026, 12:41 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-2cp6-34r9-54xx

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-2cp6-34r9-54xx

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# Patch Next advisory brief: CVE-2026-24888

Advisory: Maker.js has Unsafe Property Copying in makerjs.extendObject
IDs: CVE-2026-24888, GHSA-2cp6-34r9-54xx
Record: https://patchnext.com/advisories/cve-2026-24888 (revision 2, source checked 26 Oct 2026, 12:41 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: makerjs 0.19.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm makerjs: affected <= 0.19.1; fixed in 0.19.2

## Suggested inspection (read-only)
- `npm ls makerjs --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 makerjs.
- 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-2cp6-34r9-54xx (OSV record GHSA-2cp6-34r9-54xx lists affected ranges: npm makerjs >=0 <0.19.2 (fixed))
- Verified: https://github.com/advisories/GHSA-2cp6-34r9-54xx (GitHub-reviewed advisory GHSA-2cp6-34r9-54xx lists affected ranges: npm makerjs >=0 <=0.19.1)

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