A prototype pollution vulnerability exists in the function copy in dom.js in the xmldom (published as @xmldom/xmldom) package before 0.8.3 for Node.js via the p variable. NOTE: the vendor states "we are in the process of marking this report as invalid"; however, some third parties takes the position that "A prototype injection/Prototype pollution is not just when global objects are polluted with recursive merge or deep cloning but also when a target object is polluted."

xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. xmldom parses XML that is not well-formed because it contains multiple top level elements, and adds all root nodes to the childNodes collection of the Document, without reporting any error or throwing. This breaks the assumption that there is only a single root node in the tree, which led to issuance of CVE-2022-39299 as it is a potential issue for dependents. Update to @xmldom/xmldom@~0.7.7, @xmldom/xmldom@~0.8.4 (dist-tag latest) or @xmldom/xmldom@>=0.9.0-beta.4 (dist-tag next). As a workaround, please one of the following approaches depending on your use case: instead of searching for elements in the whole DOM, only search in the documentElementor reject a document with a document that has more then 1 childNode.

Impact xmldom versions 0.6.0 and older do not correctly escape special characters when serializing elements removed from their ancestor. This may lead to unexpected syntactic changes during XML processing in some downstream applications.

Patches Update to one of the fixed versions of @xmldom/xmldom (>=0.7.0)

See issue #271 for the status of publishing xmldom to npm or join #270 for Q&A/discussion until it's resolved.

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/ - https://mattermost.com/blog/securing-xml-implementations-across-the-web/

For more information

If you have any questions or comments about this advisory:

Open an issue in xmldom/xmldom Email us: send an email to all addresses that are shown by npm owner ls @xmldom/xmldom

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.