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Fencer Vulns
medium 4.3

CVE-2021-21366 json

Misinterpretation of malicious XML input

published 2021-03-12 5 y ago modified 2026-09-10 1 mo ago also GHSA-h6q6-9hqw-rwfv , EUVD-2021-0663

cvss
4.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.3%
EPSS 1.3% chance of exploitation in 30 days, percentile 71%
public exploits
0
none known

Summary

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.

Patch / fix

  • npm xmldom 0.5.0
  • xmldom_project xmldom 0.5.0
  • node-xmldom Debian 14, Debian 13, Debian 12 0.5.0-1

debian advisories DEBIAN-CVE-2021-21366

  • node-xmldom Ubuntu 20.04 LTS 0.1.27+ds-1+deb10u2build0.20.04.1

ubuntu advisories UBUNTU-CVE-2021-21366

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-21366 updated cvss 4.3

xmldom: incorrect parsing and serialization leads to unexpected behavior

  • Red Hat OpenShift Container Platform 3.11 openshift3/ose-console Red Hat OpenShift Container Platform 4 openshift4/ose-console
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.34% chance of exploitation in the next 30 days, higher than 71% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
NVD 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:N/I:P/A:N
GitHub 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

Affected packages

ecosystem package affected fixed in
npm xmldom
<0.5.0
0.5.0

Affected products

  • xmldom xmldom

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.