CVE-2021-21366

Name: CVE-2021-21366
Creator: NVD / NIST
Published: 2021-03-12T17:15:12.643+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.3/10EPSS 1.33%

Last modified Jun 17, 2026

CVE-2021-21366 is a medium-severity vulnerability rated 4.3/10 on the CVSS scale. xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. xmldom versions 0.4.0 and older do not correctly preserve system identifiers, FPIs or namespaces when repeatedly parsing and serializing maliciously crafted documents. EPSS estimates a 1.33% chance of exploitation in the next 30 days.

Description

xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. xmldom versions 0.4.0 and older do not correctly preserve system identifiers, FPIs or namespaces when repeatedly parsing and serializing maliciously crafted documents. This may lead to unexpected syntactic changes during XML processing in some downstream applications. This is fixed in version 0.5.0. As a workaround downstream applications can validate the input and reject the maliciously crafted documents.

Metrics

CVSS 3.1

4.3/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

EPSS Probability

1.33%

67.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Xmldom Project	Xmldom	< 0.5.0
Debian	Debian Linux	10.0

References

https://github.com/xmldom/xmldom/commit/d4201b9dfbf760049f457f9f08a3888d48835135Patch
https://github.com/xmldom/xmldom/releases/tag/0.5.0Release Notes
https://github.com/xmldom/xmldom/security/advisories/GHSA-h6q6-9hqw-rwfvVendor Advisory
https://lists.debian.org/debian-lts-announce/2023/01/msg00000.htmlMailing List, Third Party Advisory
https://www.npmjs.com/package/xmldomProduct
https://github.com/xmldom/xmldom/commit/d4201b9dfbf760049f457f9f08a3888d48835135Patch
https://github.com/xmldom/xmldom/releases/tag/0.5.0Release Notes
https://github.com/xmldom/xmldom/security/advisories/GHSA-h6q6-9hqw-rwfvVendor Advisory
https://lists.debian.org/debian-lts-announce/2023/01/msg00000.htmlMailing List, Third Party Advisory
https://www.npmjs.com/package/xmldomProduct

Timeline

Published: Mar 12, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-21366?

How severe is CVE-2021-21366?

CVE-2021-21366 has a CVSS score of 4.3/10 (MEDIUM severity). The EPSS model estimates a 1.33% probability of exploitation in the next 30 days.

How do I fix CVE-2021-21366?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-21366?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST