CVE-2021-43855: Stored XSS via SVG in Requarks/wiki

Severity: medium (CVSS 5.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.9% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2021-12-27 · updated 2026-06-17
Weakness: CWE-79

Description

Wiki.js is a wiki app built on node.js. Wiki.js 2.5.263 and earlier is vulnerable to stored cross-site scripting through a SVG file upload made via a custom request with a fake MIME type. By creating a crafted SVG file, a malicious Wiki.js user may stage a stored cross-site scripting attack. This allows the attacker to execute malicious JavaScript when the SVG is viewed directly by other users. Scripts do not execute when loaded inside a page via normal `<img>` tags. The malicious SVG can only be uploaded by crafting a custom request to the server with a fake MIME type. A patch in version 2.5.264 fixes this vulnerability by adding an additional file extension verification check to the optional (enabled by default) SVG sanitization step to all file uploads that match the SVG mime type. As a workaround, disable file upload for all non-trusted users.

Affected products

Requarks wiki: before 2.5.264 — fixed in 2.5.264

How to fix

Upgrade to a fixed version: Requarks wiki 2.5.264. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2021-43855 or the next vulnerability affects your stack