Access of Resource Using Incompatible Type in Hermes

Exploitation

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

CVSS

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

EPSS

• CVE-2021-24044: 1.26% estimated exploitation activity in the next 30 days; percentile 69.65 (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.

By passing invalid javascript code where await and yield were called upon non-async and non-generator getter/setter functions, Hermes would invoke generator functions and error out on invalid await/yield positions. This could result in segmentation fault as a consequence of type confusion error, with a low chance of RCE. This issue affects Hermes versions prior to v0.10.0.

Published by the source

16 Jan 2022, 00:00 UTC

Last modified by the source

8 Nov 2023, 04:05 UTC

Source last checked

26 Oct 2026, 12:16 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-7mhc-prgv-r3q4

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-7mhc-prgv-r3q4

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2021-24044

Advisory: Access of Resource Using Incompatible Type in Hermes
IDs: CVE-2021-24044, GHSA-7mhc-prgv-r3q4
Record: https://patchnext.com/advisories/cve-2021-24044 (revision 2, source checked 26 Oct 2026, 12:16 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: hermes-engine 0.10.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm hermes-engine: affected <= 0.9.0; fixed in 0.10.0

## Suggested inspection (read-only)
- `npm ls hermes-engine --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 hermes-engine.
- 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-7mhc-prgv-r3q4 (OSV record GHSA-7mhc-prgv-r3q4 lists affected ranges: npm hermes-engine >=0 <0.10.0 (fixed))
- Verified: https://github.com/advisories/GHSA-7mhc-prgv-r3q4 (GitHub-reviewed advisory GHSA-7mhc-prgv-r3q4 lists affected ranges: npm hermes-engine >=0 <=0.9.0)

Commands are suggestions: review each one before running it.