CVE-2021-43841

Cross-site Scripting by SVG upload in xwiki-platform

Workarounds

This issue can be fixed without the patch by setting properly the configuration to download or display files, see: https://www.xwiki.org/xwiki/bin/view/Documentation/AdminGuide/Attachments#HAttachmentdisplayordownload

References

https://jira.xwiki.org/browse/XWIKI-18368

For more information

If you have any questions or comments about this advisory:

• Open an issue in Jira
• Email us at security ML

When using default XWiki configuration, it's possible for an attacker to upload an SVG containing a script executed when executing the download action on the file.

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

CVE-2021-43841 has a CVSS score of 4.1 (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 (12.10.6, 13.3RC1); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

This problem has been patched so that the default configuration doesn't allow to display the SVG files in the browser.

1. What is CVE-2021-43841? CVE-2021-43841 is a medium-severity cross-site scripting (XSS) vulnerability in org.xwiki.platform:xwiki-platform-oldcore (maven), affecting versions < 12.10.6. It is fixed in 12.10.6, 13.3RC1. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. How severe is CVE-2021-43841? CVE-2021-43841 has a CVSS score of 4.1 (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 packages are affected by CVE-2021-43841?
   • org.xwiki.platform:xwiki-platform-oldcore (maven) (versions < 12.10.6)
   • org.xwiki.platform:xwiki-platform-tool-configuration-resources (maven) (versions >= 13.0, <= 13.2)
4. Is there a fix for CVE-2021-43841? Yes. CVE-2021-43841 is fixed in 12.10.6, 13.3RC1. Upgrade to this version or later.
5. Is CVE-2021-43841 exploitable, and should I be worried? Whether CVE-2021-43841 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-2021-43841 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-2021-43841?
   • Upgrade org.xwiki.platform:xwiki-platform-oldcore to 12.10.6 or later
   • Upgrade org.xwiki.platform:xwiki-platform-oldcore to 13.3RC1 or later
   • Upgrade org.xwiki.platform:xwiki-platform-tool-configuration-resources to 13.3RC1 or later
   • Upgrade org.xwiki.platform:xwiki-platform-tool-configuration-resources to 12.10.6 or later

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