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MikroormApplication · Mikro Orm

CVE-2026-34221

CRITICAL · 9.1 CVSS v3.1 Published 2026-03-31
Fix available
A fix is available. Upgrade to 6.6.10 / 7.0.6 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

MikroORM's Utils.merge helper function lacks sanitization for special JavaScript object keys (__proto__, constructor, prototype), allowing an attacker to inject these keys through user-controlled input and modify the Object.prototype. This prototype pollution can lead to denial of service or potentially remote code execution depending on application logic.

MitigationUpgrade MikroORM to version 6.6.10 or 7.0.6 or later to receive the patch that filters dangerous keys during object merging.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
MikroormApplication
Affected:< 6.6.10>= 7.0.0, < 7.0.6

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify MikroORM version
    Run 'npm list mikroorm' or check package.json dependencies to see the installed version of MikroORM
    Affected if The installed version is less than 6.6.10 for the 6.x branch, or between 7.0.0 and 7.0.5 for the 7.x branch
  2. Locate Utils.merge usage
    Search codebase for calls to Utils.merge, orm.utils.merge, or import statements referencing the merge helper from MikroORM packages
    Affected if The application imports and invokes the merge helper function from MikroORM's Utils module
  3. Audit merge input sources
    Review all code paths where data is passed to merge() and identify whether any source (request body, API input, file parsing, database queries) could contain object keys named __proto__, constructor, or prototype
    Affected if User-controlled or external data flows into merge() calls without sanitizing object property names
  4. Check for dynamic object key assignment
    Inspect merge() call arguments to see if any are constructed dynamically from external sources, especially where object spread operators or Object.assign are used with untrusted input
    Affected if The merge function receives objects whose keys derive from untrusted sources and include special JavaScript property names

You are affected if your MikroORM version is below 6.6.10 or between 7.0.0 and 7.0.5 AND your application passes external input to the Utils.merge function without filtering special property names.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 6.6.10 / 7.0.6 or later
Fixed in 6.6.107.0.6
Interim mitigation

Upgrade MikroORM to version 6.6.10 or 7.0.6 or later to receive the patch that filters dangerous keys during object merging.

Recommended fix High confidence

6.6.10 (for v6.x users) or 7.0.6 (for v7.x users)

  1. Identify your current MikroORM version by checking package.json
  2. If using MikroORM v6.x: run `npm install mikroorm@^6.6.10` or `npm update mikroorm`
  3. If using MikroORM v7.x: run `npm install mikroorm@^7.0.6` or `npm update mikroorm`
  4. Verify the upgrade was successful by running `npm list mikroorm`
  5. Test that your application functions correctly after the upgrade
Caveat Minor/patch releases typically contain no breaking changes; however, review MikroORM release notes for any migration notes

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Mikroorm Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing3.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,210
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-34221 in production — separate from our analysis above.

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What this is

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What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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  • No spam, self-promotion, credentials, or personal data