GHSA-42fc-7w97-8vrc — medium GitHub Advisory (CVE-2026-42140) in maven/org.xwiki.contrib.plantuml:m…

Description

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.

Basic information

Type: reviewed
Severity: medium
Advisory on GitHub: Open advisory ↗
Repository advisory: Open repository advisory ↗
Source code: Browse source ↗
Published (advisory): 2026-05-05 19:32:57 UTC
Updated: 2026-05-05 19:32:58 UTC
GitHub reviewed: 2026-05-05 19:32:57 UTC
NVD published: 2026-05-04

Score	Percentile
0.03%	6.95%

CVSS Scores

Base score	Version	Severity	Vector
4.4	3.1	—	`CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:L/I:L/A:N` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:H) Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:R) A real person has to do something—click, install, enable—otherwise it doesn’t land. Scope (S:C) Breaking this can reach past the original component and bite other resources—bigger blast radius. Confidentiality (C:L) Some sensitive info could get out, but not a total data dump. Integrity (I:L) Attackers could change some data, but it’s limited—not everything goes. Availability (A:N) Service keeps running; no real outage angle.

Identifiers

Type	Value
GHSA	GHSA-42fc-7w97-8vrc ↗
CVE	CVE-2026-42140 ↗

CWEs

CWE id	Name
CWE-918	Server-Side Request Forgery (SSRF)

Credits

lukasz-rybak (reporter)

Affected packages (1)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem	Package	Vulnerable range	First patched	Vulnerable functions
maven	org.xwiki.contrib.plantuml:macro-plantuml-macro	< 2.4.1	2.4.1	—

XWiki PlantUML Macro Vulnerable to Server-Side Request Forgery (SSRF) via 'server' parameter