How severe is CVE-2026-30241?

No CVSS score has been assigned to CVE-2026-30241 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-30241?

CVE-2026-30241 affects the following packages: mercurius (npm). Ecosystems affected: npm.

How do I fix CVE-2026-30241?

Update mercurius to 16.8.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-30241 is resolved across your whole dependency graph.

How do I detect CVE-2026-30241 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mercurius, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-30241 if there is no patch (or I can't update yet)?

Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Is CVE-2026-30241 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-30241 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-30241?

CVE-2026-30241 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 31th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-30241?

CVE-2026-30241 is classified as CWE-863 (CWE-863). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-30241 published, and has it been updated?

CVE-2026-30241 was published on March 6, 2026 and was last updated on October 21, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2026-30241: mercurius DoS

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-30241.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk-0.06%

Lower risk than most CVEs31th percentile — riskier than 31% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

90other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

mercuriusnpm

124Kdownloads / week

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.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`mercurius`	all versions	16.8.0`npm install mercurius@16.8.0`

Affected Products

1 product · 1 configurations

Application

mercuriusmercurius_project

< 16.8.0

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mercurius, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update mercurius to 16.8.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-30241 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

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

O3 Security · Impact-Aware SCA

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CVE-2026-30241 — mercurius