CVE-2021-23124Network attack vector

Cross-site scripting via unescaped aria-label

Published Jan 12, 2021 · Updated Feb 25, 2026

Cross-site scripting in Joomla! CMS 3.9.0 through 3.9.23 allows remote attackers to execute script in a victim's browser via crafted breadcrumb data. The mod_breadcrumbs module inserts attacker-influenced text into the aria-label attribute without HTML escaping, allowing script markup to execute when the page is rendered. Exploitation requires a victim to load the affected page; the consequence is browser-side content manipulation and data access within that user's session.

CVSS severity6.1
Medium
EPSS probability78.96%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Cross-site scripting in Joomla! CMS 3.9.0 through 3.9.23 allows remote attackers to execute script in a victim's browser via crafted breadcrumb data. The mod_breadcrumbs module inserts attacker-influenced text into the aria-label attribute without HTML escaping, allowing script markup to execute when the page is rendered. Exploitation requires a victim to load the affected page; the consequence is browser-side content manipulation and data access within that user's session.

The record

CVE
CVE-2021-23124
Published
Jan 12, 2021
Updated
Feb 25, 2026
Vendor
Joomla! Project
Product
Joomla! CMS
Classifications
CWE-79, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 12, 2021CVE publishedPublication date reported by the CVE source.
  2. Feb 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.9.0-3.9.23

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Joomla! Project · Joomla! CMSversion=3.9.0-3.9.23

Published CVSS scores

4.3NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1189Drive-by Compromise

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo