# CVE-2021-23383: Prototype Pollution

> Attackers can pollute prototypes in Handlebars templates from untrusted sources, potentially leading to code execution or privilege escalation.

- **Severity:** Medium 5.6 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L/E:P/RL:O/RC:C`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 May 2021
- **Updated:** 8 Oct 2026
- **Also known as:** DEBIAN-CVE-2021-23383, GHSA-765h-qjxv-5f44, MINI-3242-7cjj-mjqg, MINI-jp48-642j-mjx2, OESA-2021-1196, ROOT-APP-NPM-CVE-2021-23383, UBUNTU-CVE-2021-23383

## What is CVE-2021-23383?

CVE-2021-23383 is a medium-severity vulnerability in Netapp E-Series Performance Analyzer, published on 4 May 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The package handlebars before 4.7.7 are vulnerable to Prototype Pollution when selecting certain compiling options to compile templates coming from an untrusted source.

Weakness: CWE-1321 (Improperly Controlled Modification of Object Prototype Attributes)

## Which versions are affected by CVE-2021-23383?

2 open source packages ship an affected version, including handlebars. It affects 2 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `handlebars` | npm | All versions | 4.7.7 |
| `handlebars` | npm | All versions | 4.7.7 |

Products: Handlebarsjs Handlebars, Netapp E-Series Performance Analyzer.

## How do I fix CVE-2021-23383?

Upgrade handlebars to 4.7.7 or later.

## Is CVE-2021-23383 being exploited?

There is no known exploitation of CVE-2021-23383 in the wild and no public exploit code.

Public exploit code:

- The package handlebars before 4.7.7 are vulnerable to Prototype Pollution when selecting certain compiling options to compile templates coming from an untrusted source. (github_poc): https://github.com/fazilbaig1/CVE-2021-23383
- Check the conditions for exploiting CVE-2021-23383 through the handlebars library version assessment. (github_poc): https://github.com/dn9uy3n/Check-CVE-2021-23383

## Other vulnerabilities in Netapp E-Series Performance Analyzer

- [CVE-2026-33937](https://insights.sbomify.com/CVE-2026-33937/): Handlebars.js has JavaScript Injection via AST Type Confusion (critical 9.8)
- [CVE-2026-33941](https://insights.sbomify.com/CVE-2026-33941/): Handlebars.js has JavaScript Injection in CLI Precompiler via Unescaped Names and Options (high 8.3)
- [CVE-2026-33938](https://insights.sbomify.com/CVE-2026-33938/): Handlebars.js has JavaScript Injection via AST Type Confusion by tampering @partial-block (high 8.1)
- [CVE-2026-33940](https://insights.sbomify.com/CVE-2026-33940/): Handlebars.js has JavaScript Injection via AST Type Confusion when passing an object as dynamic partial (high 8.1)
- [CVE-2019-20920](https://insights.sbomify.com/CVE-2019-20920/): Arbitrary Code Execution in Handlebars (high 8.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-23383 and fix it if it is affected.

What it is: CVE-2021-23383 is a medium-severity vulnerability in Netapp E-Series Performance Analyzer, published on 4 May 2021. 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-2021-23383 in the wild and no public exploit code.

Affected packages and fixed versions:
- handlebars (npm): affected all versions; fixed in 4.7.7
- handlebars (npm): affected all versions; fixed in 4.7.7

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-2021-23383/ (Markdown: https://insights.sbomify.com/CVE-2021-23383/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-23383
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-23383
- OSV: https://osv.dev/vulnerability/CVE-2021-23383

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-23383/
Summaries are generated and may contain mistakes; the official description above is the record.