What’s Vulnerable › Vulnerabilities

CVE-2021-21366: Misinterpretation of malicious XML input

• Severity: medium (CVSS 4.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-03-12 · updated 2026-06-17
• Weakness: CWE-115

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.

Affected products

• Debian Linux: 10.0
• xmldom: before 0.5.0 — fixed in 0.5.0

How to fix

Upgrade to a fixed version: xmldom 0.5.0. Check the vendor advisory for mitigations.

References

• https://github.com/xmldom/xmldom/commit/d4201b9dfbf760049f457f9f08a3888d48835135
• https://github.com/xmldom/xmldom/releases/tag/0.5.0
• https://github.com/xmldom/xmldom/security/advisories/GHSA-h6q6-9hqw-rwfv
• https://lists.debian.org/debian-lts-announce/2023/01/msg00000.html
• https://www.npmjs.com/package/xmldom
• https://github.com/xmldom/xmldom/commit/d4201b9dfbf760049f457f9f08a3888d48835135
• https://github.com/xmldom/xmldom/releases/tag/0.5.0
• https://github.com/xmldom/xmldom/security/advisories/GHSA-h6q6-9hqw-rwfv
• https://lists.debian.org/debian-lts-announce/2023/01/msg00000.html
• https://www.npmjs.com/package/xmldom

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