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Vulnerability record · CVE-2021-43855 · published 27 December 2021

CVE-2021-43855: Requarks wiki.js cross-site scripting vulnerability

Requarks · Wiki.Js

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.

5.4 CVSS 3.1 Medium EPSS 0.89% · top 42.3% CWE-79 · Cross-site scripting
5.4CVSS 3.1 base score, v2 3.5
0.89%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
6References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/Requarks/wiki/commit/57b56d3a5b9c00358814e76f3ee5b4bb353ad62f PatchThird Party Advisory
https://github.com/Requarks/wiki/releases/tag/2.5.264 Release NotesThird Party Advisory
https://github.com/Requarks/wiki/security/advisories/GHSA-4893-pj5w-3hq9 ExploitPatchThird Party Advisory
https://github.com/Requarks/wiki/commit/57b56d3a5b9c00358814e76f3ee5b4bb353ad62f PatchThird Party Advisory
https://github.com/Requarks/wiki/releases/tag/2.5.264 Release NotesThird Party Advisory
https://github.com/Requarks/wiki/security/advisories/GHSA-4893-pj5w-3hq9 ExploitPatchThird Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2021-43855), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.