How severe is CVE-2026-34221?

No CVSS score has been assigned to CVE-2026-34221 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-34221?

CVE-2026-34221 affects the following packages: @mikro-orm/core (npm), @mikro-orm/core (npm). Ecosystems affected: npm.

How do I fix CVE-2026-34221?

Update @mikro-orm/core to 6.6.10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34221 is resolved across your whole dependency graph.

How do I detect CVE-2026-34221 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @mikro-orm/core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-34221 if there is no patch (or I can't update yet)?

Until you can upgrade, make sure every query built from user input uses parameterised statements or a prepared-statement API rather than string concatenation, and reduce the database account's privileges so an injected query cannot read or alter data beyond what the feature needs.

Is CVE-2026-34221 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-34221 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-34221?

CVE-2026-34221 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 33th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-34221?

CVE-2026-34221 is classified as CWE-1321 (CWE-1321). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-34221 published, and has it been updated?

CVE-2026-34221 was published on March 31, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

Not in CISA KEV

CVE-2026-34221 — @mikro-orm/core

CVE-2026-34221 is a CWE-1321 vulnerability in @mikro-orm/core. A fix is available for @mikro-orm/core — see the affected versions and patch details below.

MikroORM has Prototype Pollution in Utils.merge

Also known asGHSA-qpfv-44f3-qqx6

Published

Mar 31, 2026

Updated

Oct 28, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-34221.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs33th percentile — riskier than 33% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

2 pkgs affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

309other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

@mikro-orm/corenpm

1.5Mdownloads / week

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.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`@mikro-orm/core`	all versions	6.6.10`npm install @mikro-orm/core@6.6.10`
📦npm	`@mikro-orm/core`	≥ 7.0.0-dev.0&&< 7.0.6	7.0.6`npm install @mikro-orm/core@7.0.6`

Affected Products

1 product · 2 configurations

Application

mikroormmikro-orm

≥ 7.0.0 && < 7.0.6

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @mikro-orm/core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @mikro-orm/core to 6.6.10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34221 is resolved across your whole dependency graph.
Workarounds
Until you can upgrade, make sure every query built from user input uses parameterised statements or a prepared-statement API rather than string concatenation, and reduce the database account's privileges so an injected query cannot read or alter data beyond what the feature needs.

Frequently Asked Questions

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

O3 Security · Impact-Aware SCA

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