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Fencer Vulns
medium 6.1

CVE-2021-26035 json

[20210701] - Core - XSS in JForm Rules field

published 2021-07-07 5 y ago modified 2026-09-08 2 mo ago also BIT-joomla-2021-26035 , EUVD-2021-12858

cvss
6.1
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 54%
public exploits
0
none known

Summary

An issue was discovered in Joomla! 3.0.0 through 3.9.27. Inadequate escaping in the rules field of the JForm API leads to a XSS vulnerability.

Exploit prediction

0.72% chance of exploitation in the next 30 days, higher than 54% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:N/I:P/A:N
OSV 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
bitnami joomla
>=3.0.0, <=3.9.27
no fix listed

Affected products

  • Joomla! Project Joomla! CMS

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.