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CRITICAL severity

CVE-2021-24044 — hermes-engine

CRITICAL

CVE-2021-24044 is a critical-severity (CVSS 9.8) CWE-843 vulnerability in hermes-engine. A fix is available for hermes-engine — see the affected versions and patch details below.

Access of Resource Using Incompatible Type in Hermes

Also known asGHSA-7mhc-prgv-r3q4
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.3%probability of exploitation in next 30 days
Lower Risk+0.04%
Lower risk than most CVEs71th percentile — riskier than 71% of all scored CVEsHighest risk
0.00%0.60%1.20%1.80%0.5%1.3%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, a proxy for how much of the ecosystem is exposed.

hermes-enginenpm
182Kdownloads / week

Description

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.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npmhermes-engineall versions0.10.0npm install hermes-engine@0.10.0

Affected Products

1 product · 1 configurations
Application
hermesfacebook
< 0.10.0
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for hermes-engine, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update hermes-engine to 0.10.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-24044 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

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.
O3 Security · Impact-Aware SCA

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CVE-2021-24044: hermes-engine RCE — Fixed in 0.10.0