Patch-Source: https://github.com/libexpat/libexpat/commit/a2fe525e660badd64b6c557c2b1ec26ddc07f6e4 From a2fe525e660badd64b6c557c2b1ec26ddc07f6e4 Mon Sep 17 00:00:00 2001 From: Sebastian Pipping Date: Sat, 12 Feb 2022 01:09:29 +0100 Subject: [PATCH] lib: Protect against malicious namespace declarations (CVE-2022-25236) --- expat/lib/xmlparse.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/expat/lib/xmlparse.c b/expat/lib/xmlparse.c index c768f856..a3aef88c 100644 --- a/lib/xmlparse.c +++ b/lib/xmlparse.c @@ -3754,6 +3754,17 @@ addBinding(XML_Parser parser, PREFIX *prefix, const ATTRIBUTE_ID *attId, if (! mustBeXML && isXMLNS && (len > xmlnsLen || uri[len] != xmlnsNamespace[len])) isXMLNS = XML_FALSE; + + // NOTE: While Expat does not validate namespace URIs against RFC 3986, + // we have to at least make sure that the XML processor on top of + // Expat (that is splitting tag names by namespace separator into + // 2- or 3-tuples (uri-local or uri-local-prefix)) cannot be confused + // by an attacker putting additional namespace separator characters + // into namespace declarations. That would be ambiguous and not to + // be expected. + if (parser->m_ns && (uri[len] == parser->m_namespaceSeparator)) { + return XML_ERROR_SYNTAX; + } } isXML = isXML && len == xmlLen; isXMLNS = isXMLNS && len == xmlnsLen;