Prototype Pollution in mixme

Exploitation

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

CVSS

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

EPSS

• CVE-2021-28860: 1.84% estimated exploitation activity in the next 30 days; percentile 79.04 (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.

Node.js mixme 0.5.0, an attacker can add or alter properties of an object via 'proto' through the mutate() and merge() functions. The polluted attribute will be directly assigned to every object in the program. This will put the availability of the program at risk causing a potential denial of service (DoS).

Published by the source

6 May 2021, 15:45 UTC

Last modified by the source

10 Sep 2026, 03:49 UTC

Source last checked

24 Oct 2026, 04:13 UTC

1. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-r5cq-9537-9rpf

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-79jw-6wg7-r9g4

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# Patch Next advisory brief: CVE-2021-28860

Advisory: Prototype Pollution in mixme
IDs: CVE-2021-28860, GHSA-79jw-6wg7-r9g4
Record: https://patchnext.com/advisories/cve-2021-28860 (revision 2, source checked 24 Oct 2026, 04:13 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: mixme 0.5.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm mixme: affected < 0.5.1; fixed in 0.5.1

## Suggested inspection (read-only)
- `npm ls mixme --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 mixme.
- 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-79jw-6wg7-r9g4 (OSV record GHSA-79jw-6wg7-r9g4 lists affected ranges: npm mixme >=0 <0.5.1 (fixed))
- Verified: https://osv.dev/vulnerability/GHSA-r5cq-9537-9rpf (OSV record GHSA-r5cq-9537-9rpf lists affected ranges: npm mixme >=0 <0.5.1 (fixed))

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