CVE-2026-30241: Mercurius is a GraphQL adapter for Fastify. Prior to version 16.8.0, Mercurius fails to enforce the configured queryDepth limit on GraphQL subscriptio...

Description

Mercurius is a GraphQL adapter for Fastify. Prior to version 16.8.0, Mercurius fails to enforce the configured queryDepth limit on GraphQL subscription queries received over WebSocket connections. The depth check is correctly applied to HTTP queries and mutations, but subscription queries are parsed and executed without invoking the depth validation. This allows a remote client to submit arbitrarily deeply nested subscription queries over WebSocket, bypassing the intended depth restriction. On schemas with recursive types, this can lead to denial of service through exponential data resolution on each subscription event. This issue has been patched in version 16.8.0.

Metrics

CVSS 3.1

8.2/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

CVSS 4.0

2.7/10

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability

0.36%

28.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-863

Affected Software

Vendor	Product	Versions
Mercurius Project	Mercurius	< 16.8.0

References

Timeline

Published: Mar 6, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-30241?

Mercurius is a GraphQL adapter for Fastify. Prior to version 16.8.0, Mercurius fails to enforce the configured queryDepth limit on GraphQL subscription queries received over WebSocket connections. The depth check is correctly applied to HTTP queries and mutations, but subscription queries are parsed and executed without invoking the depth validation. This allows a remote client to submit arbitrarily deeply nested subscription queries over WebSocket, bypassing the intended depth restriction. On schemas with recursive types, this can lead to denial of service through exponential data resolution on each subscription event. This issue has been patched in version 16.8.0.

How severe is CVE-2026-30241?

CVE-2026-30241 has a CVSS score of 2.7/10 (LOW severity). The EPSS model estimates a 0.36% probability of exploitation in the next 30 days.

How do I fix CVE-2026-30241?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.