CVE-2021-43801: Uncaught Exception in mercurius

Severity: medium (CVSS 5.0 v2.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-12-13 · updated 2026-06-17
Weakness: CWE-754

Description

Mercurius is a GraphQL adapter for Fastify. Any users from Mercurius@8.10.0 to 8.11.1 are subjected to a denial of service attack by sending a malformed JSON to `/graphql` unless they are using a custom error handler. The vulnerability has been fixed in https://github.com/mercurius-js/mercurius/pull/678 and shipped as v8.11.2. As a workaround users may use a custom error handler.

Affected products

mercurius-js mercurius: from 8.10.0 before 8.11.2 — fixed in 8.11.2

How to fix

Upgrade to a fixed version: mercurius-js mercurius 8.11.2. Check the vendor advisory for mitigations.

References

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