CVE-2021-21366

mediumpriority · track · 17EPSS 0.013 · 71 %ileEUUS

grimoire priorityP3 · Track

Exploitable?

—

no known exploitation

Likely / severe?

1.34% (71st) EPSS

CVSS 4.3 · medium

Is it mine?

4 products

Check your exposure

Who says so?

4 sources

cnnvd · enisa_euvd · nvd · osv

EPSS · scored 2026-10-27

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.

cvss

Technical severity, 0–10. One row per scoring source.

4.3

010

base score 0–10 · higher = more severe · hover a vector to decode

v2.04.3mediumAV:N/AC:M/Au:N/C:N/I:P/A:Nprimary · NVD / NIST USexploitability 8.6 · impact 2.9

v3.14.3mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:Nprimary · NVD / NIST USexploitability 2.8 · impact 1.4

v3.14.3mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:Nsecondary · ENISA EU

v3.14.3mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:Nsecondary · security-advisories@github.comexploitability 2.8 · impact 1.4

v3.14.3mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:Nsecondary · OSV

v3.14mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N/E:Usecondary · CVSS-BT (t0sche)

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-436USprimaryCWE-115USCWE-115USCWE-436US

affected products (4)

Products and version ranges known to be affected.

xmldom xmldom≤ < 0.5.0enisa_euvdEU
debian debian linux= 10.0nvdUScpe:2.3:o:debian:debian_linux:*:*:*:*:*:*:*:*
xmldom project xmldom< 0.5.0nvdUScpe:2.3:a:xmldom_project:xmldom:*:*:*:*:*:*:*:*
npm xmldom< 0.5.0osvUSpkg:npm/xmldom

advisories (1)

Vendor and ecosystem advisories describing this.

GHSA-h6q6-9hqw-rwfvMisinterpretation of malicious XML input2021-03-12ghsa · osvUS
### Impact xmldom versions 0.4.0 and older do not correctly preserve [system identifiers](https://www.w3.org/TR/2008/REC-xml-20081126/#d0e4313), [FPIs](https://en.wikipedia.org/wiki/Formal_Public_Identifier) or [namespaces](https://www.w3.org/TR/xml-names11/) when repeatedly parsing and serializing maliciously crafted documents. This may lead to unexpected syntactic changes during XML processing in some downstream applications. ### Patches Update to 0.5.0 (once it is released) ### Workarounds Downstream applications can validate the input and reject the maliciously crafted documents. ### References Similar to this one reported on the Go standard library: - https://mattermost.com/blog/coordinated-disclosure-go-xml-vulnerabilities/ ### For more information If you have any questions or comments about this advisory: * Open an issue in [`xmldom/xmldom`](https://github.com/xmldom/xmldom) * Email us: send an email to **all** addresses that are shown by `npm owner ls xmldom`

also known as (3)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd nvd osv NVD CVE.org MITRE

published 2021-03-12modified 2026-06-17

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references (20)

External citations — patches, advisories, analysis.

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