CSRF in Mercurius-Js Mercurius
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.
Vulnerability class: CSRF (Cross-Site Request Forgery)
EPSS: 0.002 (5.5th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N.
Affected products
- Mercurius-js Mercurius — versions < 16.4.0
- Mercurius_project Mercurius
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Patch, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC, Issue Tracking)
- security-advisories@github.com (Patch, x_refsource_MISC)
Frequently asked questions
- What is CVE-2025-64166?
- CVE-2025-64166 is a medium-severity vulnerability in Mercurius-Js Mercurius, classified under Cross-Site Request Forgery (CSRF). CVSS score: 5.4/10. Published 2026-03-05.
- How severe is CVE-2025-64166?
- Medium severity. CVSS v3 base score is 5.4 out of 10.