CVE-2026-42140: Server-Side Request Forgery (SSRF) in PlantUML Macro via 'server' parameter
Impact
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.
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.
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.
Other sources
PlantUML Macro is a macro for rendering UML diagrams from simple textual schemes. Prior to version 2.4.1, 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 has been patched in version 2.4.1.
— NVD
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-42140?
CVE-2026-42140 has a high severity due to its potential for Server-Side Request Forgery (SSRF) which can lead to unauthorized access to internal resources.
How do I fix CVE-2026-42140?
To fix CVE-2026-42140, upgrade the XWiki PlantUML Macro to version 2.4.1 or later to mitigate the vulnerability.
What does CVE-2026-42140 affect?
CVE-2026-42140 affects the XWiki PlantUML Macro versions prior to 2.4.1, specifically enabling SSRF attacks.
Who is impacted by CVE-2026-42140?
Users of the XWiki PlantUML Macro who have not upgraded past version 2.4.1 are at risk from CVE-2026-42140.
Is CVE-2026-42140 exploitable remotely?
Yes, CVE-2026-42140 is exploitable remotely as it allows attackers to send crafted requests through the vulnerable server.