How severe is CVE-2025-64166?

CVE-2025-64166 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2025-64166 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (5th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-64166?

CVE-2025-64166 affects Mercurius Project Mercurius. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-64166?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2025-64166 have an EU (EUVD) identifier?

Yes. CVE-2025-64166 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-208313.

When was CVE-2025-64166 published?

CVE-2025-64166 was published on 2026-03-05 and last updated on 2026-06-17.

CVE-2025-64166

CVE-2025-64166 is a medium-severity vulnerability in Mercurius Project Mercurius with a CVSS 3.x base score of 5.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-352.

Key facts

Severity: Medium (CVSS 3.x base score 5.4)
EPSS exploit prediction: 0% (5th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-208313
Weakness: CWE-352
Affected product: Mercurius Project Mercurius
Published: 2026-03-05
Last modified: 2026-06-17

Description

Mercurius is a GraphQL adapter for Fastify. Prior to version 16.4.0, a cross-site request forgery (CSRF) vulnerability was identified. The issue arises from incorrect parsing of the Content-Type header in requests. Specifically, requests with Content-Type values such as application/x-www-form-urlencoded, multipart/form-data, or text/plain could be misinterpreted as application/json. This misinterpretation bypasses the preflight checks performed by the fetch() API, potentially allowing unauthorized actions to be performed on behalf of an authenticated user. This issue has been patched in version 16.4.0.

Frequently asked questions

What is CVE-2025-64166?: Mercurius is a GraphQL adapter for Fastify. Prior to version 16.4.0, a cross-site request forgery (CSRF) vulnerability was identified. The issue arises from incorrect parsing of the Content-Type header in requests. Specifically, requests with Content-Type values such as application/x-www-form-urlencoded, multipart/form-data, or text/plain could be misinterpreted as application/json. This misinterpretation bypasses the preflight checks performed by the fetch() API, potentially allowing unauthorized actions to be performed on behalf of an authenticated user. This issue has been patched in version 16.4.0.
How severe is CVE-2025-64166?: CVE-2025-64166 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2025-64166 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (5th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-64166?: CVE-2025-64166 affects Mercurius Project Mercurius. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2025-64166?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-64166 have an EU (EUVD) identifier?: Yes. CVE-2025-64166 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-208313.
When was CVE-2025-64166 published?: CVE-2025-64166 was published on 2026-03-05 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:mercurius_project:mercurius:*:*:*:*:*:node.js:*:*

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