CVE-2026-34221

Description

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. Exploitation requires application code to pass untrusted user input into ORM operations that merge object structures, such as entity property assignment or query condition construction. Prototype pollution may lead to denial of service or unexpected application behavior. In certain scenarios, polluted properties may influence query construction and potentially result in SQL injection depending on application code.

How to fix CVE-2026-34221

To remediate CVE-2026-34221, upgrade the affected package to a fixed version below.

• —upgrade to 6.6.10 or later

Is CVE-2026-34221 being exploited?

Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.

Affected packages (1)

• from 0, < 6.6.10

CVSS scores

References (3)

• ADVISORYnvd.nist.gov/vuln/detail/CVE-2026-34221
• PATCHgithub.com/mikro-orm/mikro-orm
• WEBgithub.com/mikro-orm/mikro-orm/security/advisories/GHSA-qpfv-44f3-qqx6