CVE-2021-43855 Stored XSS via SVG in Requarks/wiki
A malicious user can upload a crafted SVG file to execute arbitrary JavaScript in other users' browsers when the file is viewed directly.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2021-43855?
CVE-2021-43855 is a high-severity cross-site scripting vulnerability in Requarks wiki, published on 27 Dec 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-79
Which versions are affected by CVE-2021-43855?
It affects 1 product.
Products include Requarks Wiki.js.
How do I fix CVE-2021-43855?
No fix has been published for CVE-2021-43855 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2021-43855 being exploited?
There is no known exploitation of CVE-2021-43855 in the wild and no public exploit code.
Other vulnerabilities in Requarks wiki
- CVE-2025-56643 Security feature bypass in n/a
- CVE-2026-44224 Wiki.js: Privilege Escalation via Missing Group Validation in users.update
- CVE-2020-15236 Directory Traversal in Wiki.js
- CVE-2021-43856 Stored XSS in non-image uploads in Requarks/wiki
- CVE-2022-23654 Improper write access check in Requarks/wiki
Sources
Also known as GHSA-4893-pj5w-3hq9.