CVE-2021-23597

Denial of Service (DoS)

7.5 HighFix available

This affects the package fastify-multipart before 5.3.1. By providing a name=constructor property it is still possible to crash the application. Note: This is a bypass of CVE-2020-8136 (https://security.snyk.io/vuln/SNYK-JS-FASTIFYMULTIPART-1290382).

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: High

Exploit likelihood

2.03%Up 1.1 points since Feb 13, 2022

What each source reports

CVE List Score used 7.5

Denial of Service (DoS)

Record: CVE-2021-23597
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P
Updated: 2026-11-02

EUVDEUVD-2022-1154 7.5

Record: EUVD-2022-1154
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P
Updated: 2026-11-03

GitHub AdvisoriesGHSA-qh73-qc3p-rjv2 7.5

Uncaught Exception in fastify-multipart

Impact

This is a bypass of CVE-2020-8136 (https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-8136). By providing a name=constructor property it is still possible to crash the application. The original fix only checks for the key __proto__ (https://github.com/fastify/fastify-multipart/pull/116).

All users are recommended to upgrade

Patches

v5.3.1 includes a patch

Workarounds

No workarounds are possible.

References

Read up https://www.fastify.io/docs/latest/Guides/Prototype-Poisoning/

For more information

If you have any questions or comments about this advisory:

Open an issue in https://github.com/fastify/fastify-multipart
Email us at [email protected]

Record: GHSA-qh73-qc3p-rjv2
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-400
Updated: 2026-11-02

NVD 7.5

Record: CVE-2021-23597
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 2.0: 5.0 MediumAV:N/AC:L/Au:N/C:N/I:N/A:P
Weakness: CWE-1321
Updated: 2026-11-02

OSV 7.5

Record: CVE-2021-23597
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVGHSA-qh73-qc3p-rjv2 7.5

Uncaught Exception in fastify-multipart

Impact

All users are recommended to upgrade

Patches

v5.3.1 includes a patch

Workarounds

No workarounds are possible.

References

Read up https://www.fastify.io/docs/latest/Guides/Prototype-Poisoning/

For more information

If you have any questions or comments about this advisory:

Open an issue in https://github.com/fastify/fastify-multipart
Email us at [email protected]

Record: GHSA-qh73-qc3p-rjv2
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-400
Updated: 2026-11-02

Affected products

fastify fastify-multipart

Affected packages

Affected packages
Package	Affected	Fixed
`fastify-multipart` npm	before 5.3.1	5.3.1

History

History
Recorded	Changed	Sources
Nov 3, 2026	aliases, published	EUVD
Nov 2, 2026	first indexed	CVE List, GitHub Advisories, NVD, OSV

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

In short

CVE-2021-23597 is a high vulnerability (CVSS 7.5) in Fastify Fastify-multipart, published February 11, 2022. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 2.03%, the 81st percentile. Fixed in fastify-multipart 5.3.1.