CVE-2021-21366

Misinterpretation of malicious XML input

MEDIUM
4.3
CVSS Score
Published: March 12, 2021 at 12:00 AM UTC
Updated: June 17, 2026 at 03:35 AM UTC
3 products affected across 3 vendorsDebian LinuxXmldom@xmldom

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Severity
MEDIUM4.3
Exploit prediction
EPSS 1%

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 0.5.0
Affected range stops below 0.5.0, so it looks safe — our inference, not a vendor statement
v < 0.5.0
Affected range stops below 0.5.0, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

CVSS

4.3MEDIUMGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-115CWE-436

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