CVE-2023-22477

Mercurius is vulnerable to denial of service (DoS) when using subscriptions

5.3 MediumFix available

Mercurius is a GraphQL adapter for Fastify. Any users of Mercurius until version 10.5.0 are subjected to a denial of service attack by sending a malformed packet over WebSocket to /graphql. This issue was patched in #940. As a workaround, users can disable subscriptions.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: None
Availability: Low

Exploit likelihood

1.09%Up 0.1 points since Jan 10, 2023

What each source reports

CVE List Score used 5.3

Mercurius is vulnerable to denial of service (DoS) when using subscriptions

Record: CVE-2023-22477
CVSS 3.1: 5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness: CWE-248
Updated: 2026-11-02

EUVDEUVD-2023-0446 5.3

Record: EUVD-2023-0446
CVSS 3.1: 5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Updated: 2026-11-02

GitHub AdvisoriesGHSA-cm8h-q92v-xcfc 5.3

mercurius has Uncaught Exception when using subscriptions

Impact

Any users of Mercurius until version v11.5.0 are subjected to a denial of service attack by sending a malformed packet over WebSocket to /graphql.

Patches

This was patched in https://github.com/mercurius-js/mercurius/pull/940. The patch was released as v11.5.0 and v8.13.2.

Workarounds

Disable subscriptions.

References

Reported publicly as https://github.com/mercurius-js/mercurius/issues/939. The same problem was solved in https://github.com/fastify/fastify-websocket/pull/228

Record: GHSA-cm8h-q92v-xcfc
CVSS 3.1: 5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness: CWE-248
Updated: 2026-11-02

NVD 5.3

Record: CVE-2023-22477
CVSS 3.1: 5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-248
Updated: 2026-11-02

OSV 5.3

Mercurius is vulnerable to denial of service (DoS) when using subscriptions

Record: CVE-2023-22477
CVSS 3.1: 5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness: CWE-248
Updated: 2026-11-02

OSVGHSA-cm8h-q92v-xcfc 5.3

mercurius has Uncaught Exception when using subscriptions

Impact

Any users of Mercurius until version v11.5.0 are subjected to a denial of service attack by sending a malformed packet over WebSocket to /graphql.

Patches

This was patched in https://github.com/mercurius-js/mercurius/pull/940. The patch was released as v11.5.0 and v8.13.2.

Workarounds

Disable subscriptions.

References

Reported publicly as https://github.com/mercurius-js/mercurius/issues/939. The same problem was solved in https://github.com/fastify/fastify-websocket/pull/228

Record: GHSA-cm8h-q92v-xcfc
CVSS 3.1: 5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness: CWE-248
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`mercurius` npm	9.0.0 up to 11.5.0	11.5.0
`mercurius` npm	before 8.13.2	8.13.2

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2023-22477 is a medium vulnerability (CVSS 5.3) in Mercurius-js Mercurius, published January 9, 2023. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.09%, the 65th percentile. Fixed in mercurius 11.5.0.