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Fencer Vulns
high 7.6

CVE-2021-21383 json

XSS in Wiki.js

published 2021-03-18 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-8689

cvss
7.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.0%
EPSS 1.0% chance of exploitation in 30 days, percentile 62%
public exploits
0
none known

Summary

Wiki.js an open-source wiki app built on Node.js. Wiki.js before version 2.5.191 is vulnerable to stored cross-site scripting through mustache expressions in code blocks. This vulnerability exists due to mustache expressions being parsed by Vue during content injection even though it is contained within a `<pre>` element. By creating a crafted wiki page, a malicious Wiki.js user may stage a stored cross-site scripting attack. This allows the attacker to execute malicious JavaScript when the page is viewed by other users. For an example see referenced GitHub Security Advisory. Commit 5ffa189383dd716f12b56b8cae2ba0d075996cf1 fixes this vulnerability by adding the v-pre directive to all `<pre>` tags during the render.

Patch / fix

  • requarks wiki.js 2.5.191

Exploit prediction

0.97% chance of exploitation in the next 30 days, higher than 62% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/Requarks/wiki/security/advisories/GHSA-6xx4-m8gx-826r referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.6 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:H/A:N
NVD 3.1 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
NVD 2.0 3.5 AV:N/AC:M/Au:S/C:N/I:P/A:N

Affected products

  • Requarks wiki

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.