CVE-2026-83614: xmldom: Quadratic-time parsing via the malformed-input recovery path — `parseElementStartPart` re-scan and `normalize()` adjacent-text merge
xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. Prior to @xmldom/xmldom versions 0.8.15 and 0.9.12, and in xmldom versions 0.3.0 through 0.6.0, two independent quadratic paths can cause denial of service. In lib/sax.js, parseElementStartPart repeatedly rescans a malformed tag name to the next > during single-character recovery; in lib/dom.js, normalize() repeatedly removes and appends adjacent text nodes, causing quadratic reindexing and string rebuilding. The first path is reachable through default DOMParser.parseFromString() processing, while the second is also reachable through a direct normalize() call on a programmatically constructed DOM, and endDocument invokes that normalization after parsing. This issue is fixed in @xmldom/xmldom versions 0.8.15 and 0.9.12; no fixed version is available for xmldom.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
@xmldom/xmldomto a version that resolves this vulnerability.Fixed in 0.8.15 - Upgrade
Upgrade
@xmldom/xmldomto a version that resolves this vulnerability.Fixed in 0.9.12
Event History
Frequently Asked Questions
Are applications using the parser with its default behavior exposed?
Yes. The malformed-tag-name recovery path is reachable through default DOMParser.parseFromString() processing, so applications that parse attacker-controlled XML can be exposed to denial of service.
What input or access does an attacker need?
An attacker needs a way to cause processing of malformed XML that triggers the parser's single-character recovery behavior. The separate normalization path can also be triggered by calling normalize() on a programmatically constructed DOM, and parsing invokes normalization through endDocument.
Which versions contain a fix?
The issue is fixed in @xmldom/xmldom 0.8.15 and 0.9.12. No fixed version is available for the xmldom package; affected @xmldom/xmldom versions are those before 0.8.15 and 0.9.12, while xmldom 0.3.0 through 0.6.0 is affected.