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Merged
mgaffigan merged 2 commits into from
Sep 22, 2026
Merged

Harden XSLT step against XXE attacks #453

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b144bbe
Add XXE test for XSLT step (CVE-2026-78224)
mgaffigan Sep 19, 2026
883de45
Harden XSLT step against XXE attacks (CVE-2026-78224)
mgaffigan Sep 19, 2026
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195 changes: 195 additions & 0 deletions ci/tests/200-xslt-step-xxe/channels/01-xslt-xxe/channel.xml
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<channel version="4.6.0">
<id>5ec00001-0000-4000-8000-00000000c1a5</id>
<nextMetaDataId>2</nextMetaDataId>
<name>XSLT Step XXE</name>
<description></description>
<revision>1</revision>
<sourceConnector version="4.6.0">
<metaDataId>0</metaDataId>
<name>sourceConnector</name>
<properties class="com.mirth.connect.connectors.vm.VmReceiverProperties" version="4.6.0">
<pluginProperties/>
<sourceConnectorProperties version="4.6.0">
<responseVariable>None</responseVariable>
<respondAfterProcessing>true</respondAfterProcessing>
<processBatch>false</processBatch>
<firstResponse>false</firstResponse>
<processingThreads>1</processingThreads>
<resourceIds class="linked-hash-map">
<entry>
<string>Default Resource</string>
<string>[Default Resource]</string>
</entry>
</resourceIds>
<queueBufferSize>1000</queueBufferSize>
</sourceConnectorProperties>
</properties>
<transformer version="4.6.0">
<elements>
<com.mirth.connect.plugins.xsltstep.XsltStep version="4.6.0">
<name>XSLT XXE</name>
<sequenceNumber>0</sequenceNumber>
<enabled>true</enabled>
<sourceXml>connectorMessage.getRawData()</sourceXml>
<resultVariable>xsltResult</resultVariable>
<template>&apos;&lt;xsl:stylesheet version=&quot;1.0&quot; xmlns:xsl=&quot;http://www.w3.org/1999/XSL/Transform&quot;&gt;&lt;xsl:output method=&quot;text&quot;/&gt;&lt;xsl:template match=&quot;/&quot;&gt;&lt;xsl:value-of select=&quot;.&quot;/&gt;&lt;/xsl:template&gt;&lt;/xsl:stylesheet&gt;&apos;</template>
<useCustomFactory>false</useCustomFactory>
<customFactory></customFactory>
</com.mirth.connect.plugins.xsltstep.XsltStep>
</elements>
<inboundDataType>RAW</inboundDataType>
<outboundDataType>RAW</outboundDataType>
<inboundProperties class="com.mirth.connect.plugins.datatypes.raw.RawDataTypeProperties" version="4.6.0">
<batchProperties class="com.mirth.connect.plugins.datatypes.raw.RawBatchProperties" version="4.6.0">
<splitType>JavaScript</splitType>
<batchScript></batchScript>
</batchProperties>
</inboundProperties>
<outboundProperties class="com.mirth.connect.plugins.datatypes.raw.RawDataTypeProperties" version="4.6.0">
<batchProperties class="com.mirth.connect.plugins.datatypes.raw.RawBatchProperties" version="4.6.0">
<splitType>JavaScript</splitType>
<batchScript></batchScript>
</batchProperties>
</outboundProperties>
</transformer>
<filter version="4.6.0">
<elements/>
</filter>
<transportName>Channel Reader</transportName>
<mode>SOURCE</mode>
<enabled>true</enabled>
<waitForPrevious>true</waitForPrevious>
</sourceConnector>
<destinationConnectors>
<connector version="4.6.0">
<metaDataId>1</metaDataId>
<name>Destination 1</name>
<properties class="com.mirth.connect.connectors.vm.VmDispatcherProperties" version="4.6.0">
<pluginProperties/>
<destinationConnectorProperties version="4.6.0">
<queueEnabled>false</queueEnabled>
<sendFirst>false</sendFirst>
<retryIntervalMillis>10000</retryIntervalMillis>
<regenerateTemplate>false</regenerateTemplate>
<retryCount>0</retryCount>
<rotate>false</rotate>
<includeFilterTransformer>false</includeFilterTransformer>
<threadCount>1</threadCount>
<threadAssignmentVariable></threadAssignmentVariable>
<validateResponse>false</validateResponse>
<resourceIds class="linked-hash-map">
<entry>
<string>Default Resource</string>
<string>[Default Resource]</string>
</entry>
</resourceIds>
<queueBufferSize>1000</queueBufferSize>
<reattachAttachments>true</reattachAttachments>
</destinationConnectorProperties>
<channelId>none</channelId>
<channelTemplate>${message.encodedData}</channelTemplate>
<mapVariables/>
</properties>
<transformer version="4.6.0">
<elements/>
<inboundDataType>RAW</inboundDataType>
<outboundDataType>RAW</outboundDataType>
<inboundProperties class="com.mirth.connect.plugins.datatypes.raw.RawDataTypeProperties" version="4.6.0">
<batchProperties class="com.mirth.connect.plugins.datatypes.raw.RawBatchProperties" version="4.6.0">
<splitType>JavaScript</splitType>
<batchScript></batchScript>
</batchProperties>
</inboundProperties>
<outboundProperties class="com.mirth.connect.plugins.datatypes.raw.RawDataTypeProperties" version="4.6.0">
<batchProperties class="com.mirth.connect.plugins.datatypes.raw.RawBatchProperties" version="4.6.0">
<splitType>JavaScript</splitType>
<batchScript></batchScript>
</batchProperties>
</outboundProperties>
</transformer>
<responseTransformer version="4.6.0">
<elements/>
<inboundDataType>RAW</inboundDataType>
<outboundDataType>RAW</outboundDataType>
<inboundProperties class="com.mirth.connect.plugins.datatypes.raw.RawDataTypeProperties" version="4.6.0">
<batchProperties class="com.mirth.connect.plugins.datatypes.raw.RawBatchProperties" version="4.6.0">
<splitType>JavaScript</splitType>
<batchScript></batchScript>
</batchProperties>
</inboundProperties>
<outboundProperties class="com.mirth.connect.plugins.datatypes.raw.RawDataTypeProperties" version="4.6.0">
<batchProperties class="com.mirth.connect.plugins.datatypes.raw.RawBatchProperties" version="4.6.0">
<splitType>JavaScript</splitType>
<batchScript></batchScript>
</batchProperties>
</outboundProperties>
</responseTransformer>
<filter version="4.6.0">
<elements/>
</filter>
<transportName>Channel Writer</transportName>
<mode>DESTINATION</mode>
<enabled>true</enabled>
<waitForPrevious>true</waitForPrevious>
</connector>
</destinationConnectors>
<preprocessingScript>// Modify the message variable below to pre process data
return message;</preprocessingScript>
<postprocessingScript>// This script executes once after a message has been processed
// Responses returned from here will be stored as &quot;Postprocessor&quot; in the response map
return;</postprocessingScript>
<deployScript>// This script executes once when the channel is deployed
// You only have access to the globalMap and globalChannelMap here to persist data
return;</deployScript>
<undeployScript>// This script executes once when the channel is undeployed
// You only have access to the globalMap and globalChannelMap here to persist data
return;</undeployScript>
<properties version="4.6.0">
<clearGlobalChannelMap>true</clearGlobalChannelMap>
<messageStorageMode>DEVELOPMENT</messageStorageMode>
<encryptData>false</encryptData>
<encryptAttachments>false</encryptAttachments>
<encryptCustomMetaData>false</encryptCustomMetaData>
<removeContentOnCompletion>false</removeContentOnCompletion>
<removeOnlyFilteredOnCompletion>false</removeOnlyFilteredOnCompletion>
<removeAttachmentsOnCompletion>false</removeAttachmentsOnCompletion>
<initialState>STARTED</initialState>
<storeAttachments>true</storeAttachments>
<metaDataColumns>
<metaDataColumn>
<name>SOURCE</name>
<type>STRING</type>
<mappingName>mirth_source</mappingName>
</metaDataColumn>
<metaDataColumn>
<name>TYPE</name>
<type>STRING</type>
<mappingName>mirth_type</mappingName>
</metaDataColumn>
</metaDataColumns>
<attachmentProperties version="4.6.0">
<type>None</type>
<properties/>
</attachmentProperties>
<resourceIds class="linked-hash-map">
<entry>
<string>Default Resource</string>
<string>[Default Resource]</string>
</entry>
</resourceIds>
</properties>
<exportData>
<metadata>
<enabled>true</enabled>
<lastModified>
<time>1775955953073</time>
<timezone>America/Chicago</timezone>
</lastModified>
<pruningSettings>
<archiveEnabled>true</archiveEnabled>
<pruneErroredMessages>false</pruneErroredMessages>
</pruningSettings>
<userId>1</userId>
</metadata>
</exportData>
</channel>
1 change: 1 addition & 0 deletions ci/tests/200-xslt-step-xxe/channels/01-xslt-xxe/messages/01-external-entity/source
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<?xml version="1.0"?><!DOCTYPE r [<!ENTITY x SYSTEM "file:///etc/hostname">]><r>&x;</r>
1 change: 1 addition & 0 deletions ci/tests/200-xslt-step-xxe/channels/01-xslt-xxe/messages/01-external-entity/source_status
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ERROR
1 change: 1 addition & 0 deletions ci/tests/200-xslt-step-xxe/channels/01-xslt-xxe/messages/02-benign-control/source
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<?xml version="1.0"?><r>hello</r>
1 change: 1 addition & 0 deletions ci/tests/200-xslt-step-xxe/channels/01-xslt-xxe/messages/02-benign-control/source_status
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TRANSFORMED
2 changes: 1 addition & 1 deletion server/src/main/java/com/mirth/connect/plugins/xsltstep/XsltStep.java
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Expand Up @@ -70,7 +70,7 @@ private String getTransformationScript() {
script.append("transformer = tFactory.newTransformer(new Packages.javax.xml.transform.stream.StreamSource(xsltTemplate));\n");
script.append("sourceVar = new Packages.java.io.StringReader(" + sourceXml + ");\n");
script.append("resultVar = new Packages.java.io.StringWriter();\n");
script.append("transformer.transform(new Packages.javax.xml.transform.stream.StreamSource(sourceVar), new Packages.javax.xml.transform.stream.StreamResult(resultVar));\n");
script.append("transformer.transform(Packages.com.mirth.connect.util.MirthXmlUtil.getSecureSource(sourceVar), new Packages.javax.xml.transform.stream.StreamResult(resultVar));\n");

return script.toString();
}
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16 changes: 16 additions & 0 deletions server/src/main/java/com/mirth/connect/util/MirthXmlUtil.java
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Expand Up @@ -9,12 +9,14 @@

package com.mirth.connect.util;

import java.io.Reader;
import java.io.StringReader;
import java.io.StringWriter;
import java.io.Writer;
import java.util.Hashtable;

import javax.xml.XMLConstants;
import javax.xml.parsers.SAXParserFactory;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Source;
import javax.xml.transform.Templates;
Expand All @@ -24,10 +26,12 @@
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMResult;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.sax.SAXSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.xml.sax.InputSource;

public class MirthXmlUtil {

Expand Down Expand Up @@ -114,6 +118,18 @@ public static String prettyPrint(String input) {
return input;
}

/** Returns a {@link Source} for XML from an untrusted origin. */
public static Source getSecureSource(Reader reader) throws Exception {
// Use newDefaultInstance to avoid whatever is on the classpath that might
// be poisoned from the channel classloader.
SAXParserFactory factory = SAXParserFactory.newDefaultInstance();
// False by default
factory.setNamespaceAware(true);
factory.setFeature("http://apache.org/xml/features/disallow-doctype-decl", true);

return new SAXSource(factory.newSAXParser().getXMLReader(), new InputSource(reader));
}

public static String decode(String entity) {
if (entity.charAt(entity.length() - 1) == ';') // remove trailing
// semicolon
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