CVE-2021-43856: 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 non-image file uploads for fi...

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 non-image file uploads for file types that can be viewed directly inline in the browser. By creating a malicious file which can execute inline JS when viewed in the browser (e.g. XML files), a malicious Wiki.js user may stage a stored cross-site scripting attack. This allows the attacker to execute malicious JavaScript when the file is viewed directly by other users. The file must be opened directly by the user and will not trigger directly in a normal Wiki.js page. A patch in version 2.5.264 fixes this vulnerability by adding an optional (enabled by default) force download flag to all non-image file types, preventing the file from being viewed inline in the browser. As a workaround, disable file upload for all non-trusted users. --- Thanks to @Haxatron for reporting this vulnerability. Initially reported via https://huntr.dev/bounties/266bff09-00d9-43ca-a4bb-bb540642811f/

Metrics

CVSS 3.1

5.4/10

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

EPSS Probability

0.89%

54.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Requarks	Wiki.Js	< 2.5.264

References

https://github.com/Requarks/wiki/commit/79bdd4409316adf649806de3e22352297f85cee0Patch, Third Party Advisory
https://github.com/Requarks/wiki/releases/tag/2.5.264Release Notes, Third Party Advisory
https://github.com/Requarks/wiki/security/advisories/GHSA-rhpf-929m-7fm2Exploit, Patch, Third Party Advisory
https://github.com/Requarks/wiki/commit/79bdd4409316adf649806de3e22352297f85cee0Patch, Third Party Advisory
https://github.com/Requarks/wiki/releases/tag/2.5.264Release Notes, Third Party Advisory
https://github.com/Requarks/wiki/security/advisories/GHSA-rhpf-929m-7fm2Exploit, Patch, Third Party Advisory

Timeline

Published: Dec 27, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-43856?

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 non-image file uploads for file types that can be viewed directly inline in the browser. By creating a malicious file which can execute inline JS when viewed in the browser (e.g. XML files), a malicious Wiki.js user may stage a stored cross-site scripting attack. This allows the attacker to execute malicious JavaScript when the file is viewed directly by other users. The file must be opened directly by the user and will not trigger directly in a normal Wiki.js page. A patch in version 2.5.264 fixes this vulnerability by adding an optional (enabled by default) force download flag to all non-image file types, preventing the file from being viewed inline in the browser. As a workaround, disable file upload for all non-trusted users. --- Thanks to @Haxatron for reporting this vulnerability. Initially reported via https://huntr.dev/bounties/266bff09-00d9-43ca-a4bb-bb540642811f/

How severe is CVE-2021-43856?

CVE-2021-43856 has a CVSS score of 5.4/10 (MEDIUM severity). The EPSS model estimates a 0.89% probability of exploitation in the next 30 days.

How do I fix CVE-2021-43856?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.