# Prototype Pollution in handlebars

Advisory record · `GHSA-q42p-pg8m-cqh6`

- **Identifiers:** `GHSA-q42p-pg8m-cqh6`
- **State:** Confirmed
- **Severity:** CVSS 7.3 High
- **Critical:** No
- **Weakness (CWE):** [CWE-471](https://cwe.mitre.org/data/definitions/471.html)
- **Tags:** [CWE-471](https://agentprime.io/advisories/tag/cwe-471.md)
- **Published:** 5 Jun 2019
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 5 Jun 2019, 14:07 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `handlebars` (npm): affected `>=4.1.0, <4.1.2 || >=4.0.0, <4.0.14 || <3.0.7`; fixed in `4.1.2`, `4.0.14`, `3.0.7`

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 7.3 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L`, from GitHub Advisory Database

- **CISA KEV:** Not listed.
- **EPSS:** No score.

## Timeline

This record came from the full history of the GitHub Advisory Database, published 5 Jun 2019. New records show when each source confirmed them.

## Sources

- [GitHub Advisory Database: GHSA-q42p-pg8m-cqh6](https://github.com/advisories/GHSA-q42p-pg8m-cqh6)
- [OSV: GHSA-q42p-pg8m-cqh6](https://osv.dev/vulnerability/GHSA-q42p-pg8m-cqh6)
- <https://github.com/handlebars-lang/handlebars.js/issues/1495>
- <https://github.com/handlebars-lang/handlebars.js/commit/0d6d8c335ad81bad1b672fc56b6a44f6aa472dac>
- <https://github.com/handlebars-lang/handlebars.js/commit/7372d4e9dffc9d70c09671aa28b9392a1577fd86>
- <https://github.com/handlebars-lang/handlebars.js/commit/85c8783b34fc6d36145d8b53885ad0b9e3c3f9c4>
- <https://github.com/handlebars-lang/handlebars.js/commit/cd38583216dce3252831916323202749431c773e>
- <https://snyk.io/vuln/SNYK-JS-HANDLEBARS-173692>
- <https://www.npmjs.com/advisories/755>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-q42p-pg8m-cqh6>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-q42p-pg8m-cqh6/>. Everything for agents: <https://agentprime.io/llms.txt>.