XWiki PlantUML Macro Vulnerable to Server-Side Request Forgery (SSRF) via 'server' parameter
Date: 2026-05
Affected: maven/org.xwiki.contrib.plantuml:macro-plantuml-macro
Attack vector: ssrf
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2026-42140
CWE: CWE-918
CVSS: 4.4 (CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:L/I:L/A:N)

### Impact The [PlantUML Macro](https://extensions.xwiki.org/xwiki/bin/view/Extension/PlantUML+Macro) is vulnerable to Server-Side Request Forgery (SSRF). The macro allows users to specify an alternative PlantUML server via the `server` parameter. However, the application does not validate the supplied URL. An attacker can supply an internal IP address or a malicious external URL. The XWiki server will attempt to connect to this URL to "render" the diagram. This issue affects all versions of the Plant UML Macro extension till version 2.4 included. ### Patches Version 2.4.1 of the Plant UML Macro extension fixes the issue by verifying if the supplied server domain matches one of the [trusted domain configured inside of XWiki](https://www.xwiki.org/xwiki/bin/view/Documentation/AdminGuide/Configuration/#HTrusteddomains). ### Workarounds Protect the XWiki server by placing it in a DMZ so that it cannot access any other internal servers. ### Resources The issue was fixed in [PLANTUML-25](https://jira.xwiki.org/browse/PLANTUML-25) by the commit [c8b19bda93058794e04c8862fc7ca85c59b5fe5c](https://github.com/xwiki-contrib/macro-plantuml/commit/c8b19bda93058794e04c8862fc7ca85c59b5fe5c). ### For more information If there are any questions or comments about this advisory: * Open an issue in [JIRA XWiki.org](https://jira.xwiki.org/) * Send an email to [Security Mailing List](mailto:security@xwiki.org) ### Attribution The issue was reported by Łukasz Rybak.


Mitigations:

Architectural layers (MAESTRO):