# CVE-2020-1911: Access of Resource Using Incompatible Type in Facebook Hermes

> Type confusion in Hermes allows arbitrary code execution if the application evaluates untrusted JavaScript.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Sep 2020
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-f5x2-xv93-4p23

## What is CVE-2020-1911?

CVE-2020-1911 is a critical memory corruption vulnerability in Facebook Hermes, published on 4 Sep 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A type confusion vulnerability when resolving properties of JavaScript objects with specially-crafted prototype chains in Facebook Hermes prior to commit fe52854cdf6725c2eaa9e125995da76e6ceb27da allows attackers to potentially execute arbitrary code via crafted JavaScript. Note that this is only exploitable if the application using Hermes permits evaluation of untrusted JavaScript. Hence, most React Native applications are not affected.

Weakness: CWE-843 (Access of Resource Using Incompatible Type)

## Which versions are affected by CVE-2020-1911?

2 open source packages ship an affected version, including hermes-engine. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `hermes-engine` | npm | All versions | 0.5.2 |
| `hermes-engine` | npm | All versions | 0.5.2 |

Products: Facebook Hermes.

## How do I fix CVE-2020-1911?

Upgrade hermes-engine to 0.5.2 or later.

## Is CVE-2020-1911 being exploited?

There is no known exploitation of CVE-2020-1911 in the wild and no public exploit code.

## Other vulnerabilities in Facebook Hermes

- [CVE-2023-23556](https://insights.sbomify.com/CVE-2023-23556/): Memory corruption in Hermes (critical 9.8)
- [CVE-2023-23557](https://insights.sbomify.com/CVE-2023-23557/): Memory corruption in Hermes (critical 9.8)
- [CVE-2023-25933](https://insights.sbomify.com/CVE-2023-25933/): Memory corruption in Hermes (critical 9.8)
- [CVE-2023-28081](https://insights.sbomify.com/CVE-2023-28081/): Use after free in Hermes (critical 9.8)
- [CVE-2023-30470](https://insights.sbomify.com/CVE-2023-30470/): Use after free in Hermes (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-1911 and fix it if it is affected.

What it is: CVE-2020-1911 is a critical memory corruption vulnerability in Facebook Hermes, published on 4 Sep 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2020-1911 in the wild and no public exploit code.

Affected packages and fixed versions:
- hermes-engine (npm): affected all versions; fixed in 0.5.2
- hermes-engine (npm): affected all versions; fixed in 0.5.2

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2020-1911/ (Markdown: https://insights.sbomify.com/CVE-2020-1911/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-1911
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-1911
- OSV: https://osv.dev/vulnerability/CVE-2020-1911

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-1911/
Summaries are generated and may contain mistakes; the official description above is the record.