HOMEVULNERABILITIESCVE-2021-21366
MEDIUM

CVE-2021-21366

CWE-115Published: March 12, 2021· Updated: Jun 17, 2026

4.3
CVSS v3.1

Official 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.

NVD Source

Technical Analysis

CVE-2021-21366 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

Exploitation does not require any privileges, though user interaction (Required) is needed, which slightly reduces the risk of mass automated attacks.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionRequired
ScopeUnchanged
Impact
ConfidentialityNone
IntegrityLow
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

Affected Vendors & Products

Debian1 product(s)
debian linux
xmldom_project1 product(s)
xmldom
Source: NVD CPE · 2 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

PATCHhttps://github.com/xmldom/xmldom/commit/d4201b9dfbf760049f457f9f08a3888d48835135
PATCHhttps://github.com/xmldom/xmldom/commit/d4201b9dfbf760049f457f9f08a3888d48835135
ADVISORYhttps://github.com/xmldom/xmldom/security/advisories/GHSA-h6q6-9hqw-rwfv
ADVISORYhttps://lists.debian.org/debian-lts-announce/2023/01/msg00000.html
ADVISORYhttps://github.com/xmldom/xmldom/security/advisories/GHSA-h6q6-9hqw-rwfv
ADVISORYhttps://lists.debian.org/debian-lts-announce/2023/01/msg00000.html

All References (10)

→
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

Quick Facts

CVE IDCVE-2021-21366
CVSS Score4.3 / 10
SeverityMEDIUM
WeaknessCWE-115
CISA KEVNo
Affected2 vendor(s)
PublishedMar 12, 2021

Related CVEs (CWE-115)

CVE-2020-27846
9.8
CVE-2021-1587
8.6
CVE-2025-5747
8.0
CVE-2018-12116
7.5
CVE-2024-11169
7.5
CVE-2021-0207
7.5

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-21366 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.
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