CVE-2026-30241
HIGH
GHSA-m4h2-mjfm-mp55
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
Lifecycle Timeline
3Description
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.
Analysis
Mercurius versions prior to 16.8.0 fail to validate GraphQL subscription query depth limits over WebSocket connections, allowing remote attackers to bypass depth restrictions that are properly enforced for HTTP queries. An attacker can exploit this to submit arbitrarily nested subscription queries that cause denial of service through exponential data resolution on schemas with recursive types. …
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Remediation
Within 24 hours: Identify all applications using Mercurius versions prior to 16.8.0 and assess exposure. Within 7 days: Apply vendor patch to upgrade Mercurius to version 16.8.0 or later across all affected environments. …
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External POC / Exploit Code
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