CVE-2026-42140

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 by the commit c8b19bda93058794e04c8862fc7ca85c59b5fe5c.

For more information

If there are any questions or comments about this advisory:

• Open an issue in JIRA XWiki.org
• Send an email to Security Mailing List

Attribution

The issue was reported by Łukasz Rybak.

The 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.

Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.

CVE-2026-42140 has a CVSS score of 4.4 (Medium). The vector is network-reachable, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.4.1); upgrading removes the vulnerable code path.

Kodem intelligence

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.

1. What is CVE-2026-42140? CVE-2026-42140 is a medium-severity server-side request forgery (SSRF) vulnerability in org.xwiki.contrib.plantuml:macro-plantuml-macro (maven), affecting versions < 2.4.1. It is fixed in 2.4.1. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
2. How severe is CVE-2026-42140? CVE-2026-42140 has a CVSS score of 4.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of org.xwiki.contrib.plantuml:macro-plantuml-macro are affected by CVE-2026-42140? org.xwiki.contrib.plantuml:macro-plantuml-macro (maven) versions < 2.4.1 is affected.
4. Is there a fix for CVE-2026-42140? Yes. CVE-2026-42140 is fixed in 2.4.1. Upgrade to this version or later.
5. Is CVE-2026-42140 exploitable, and should I be worried? Whether CVE-2026-42140 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-42140 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-42140? Upgrade org.xwiki.contrib.plantuml:macro-plantuml-macro to 2.4.1 or later.