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.
CVE-2025-64166
MEDIUMPre-NVD 5.45.4
EchelonGraph scoreLOW confidence
This medium-severity CVE scores 5.4 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: secondary
5.4EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
- Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.4Exploit: None knownExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 5.4
- EG Score
- 5.4(low)
- EG Risk
- 29(Track)EG Risk 29/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity54% × 45%Exploitation0% × 40%Automatability30% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- 0%
- EPSS %ILE
- 6%
- KEV
- Not listed
Published
March 5, 2026
Last Modified
June 17, 2026
References (4)
- security-advisories@githubhttps://github.com/mercurius-js/mercurius/commit/962d402ec7a92342f4a1b7f5f04af01776838c3c
- security-advisories@githubhttps://github.com/mercurius-js/mercurius/pull/1187
- security-advisories@githubhttps://github.com/mercurius-js/mercurius/security/advisories/GHSA-v66j-6wwf-jc57
- 134c704f-9b21-4f2e-91b3-4a467353bcc0https://github.com/mercurius-js/mercurius/security/advisories/GHSA-v66j-6wwf-jc57
Affected Packages
(1 across 1 ecosystem)
npm(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| mercurius | — | 16.4.0 | — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 6× in last 7d / 6× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-08-01 04:15 UTCEPSS rescore
- 2026-07-30 16:27 UTCEPSS rescore
- 2026-07-30 01:30 UTCEPSS rescore
- 2026-07-28 15:35 UTCEPSS rescore
- 2026-07-27 14:12 UTCEPSS rescore
- 2026-07-27 13:51 UTCEG score recompute
Related CVEs(same CWE)
Frequently asked(5)
What is CVE-2025-64166?
CVE-2025-64166 is a medium vulnerability published on March 5, 2026. 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…
When was CVE-2025-64166 disclosed?
CVE-2025-64166 was first published in the National Vulnerability Database on March 5, 2026, with the most recent update on June 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2025-64166 actively exploited?
CVE-2025-64166 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 94.5% of all scored CVEs.
What is the CVSS score of CVE-2025-64166?
CVE-2025-64166 has a CVSS v3 base score of 5.4 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2025-64166?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2025-64166, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2025-64166
Is Your Infrastructure Affected by CVE-2025-64166?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.