CVE-2026-71573Network attack vector

Cross-origin access via origin reflection

Published Aug 18, 2026 · Updated Aug 19, 2026

Improper CORS origin validation in Joomla! CMS 4.0.0 through 5.4.7 and 6.0.0 through 6.1.2 allows attackers to bypass CORS checks via crafted Origin headers. In ApiApplication::respond() and handlePreflight(), the API layer reflected any HTTP_ORIGIN value into Access-Control-Allow-Origin and enabled credentials without checking that the request origin matched the configured cors_allow_origin whitelist. Exposure requires Joomla API CORS support to be enabled; when it is enabled, attacker-controlled sites can make browser requests appear allowed from unapproved origins, defeating the configured cross-origin policy.

CVSS severity6.9
Medium
EPSS probability0.25%
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

Improper CORS origin validation in Joomla! CMS 4.0.0 through 5.4.7 and 6.0.0 through 6.1.2 allows attackers to bypass CORS checks via crafted Origin headers. In ApiApplication::respond() and handlePreflight(), the API layer reflected any HTTP_ORIGIN value into Access-Control-Allow-Origin and enabled credentials without checking that the request origin matched the configured cors_allow_origin whitelist. Exposure requires Joomla API CORS support to be enabled; when it is enabled, attacker-controlled sites can make browser requests appear allowed from unapproved origins, defeating the configured cross-origin policy.

The record

CVE
CVE-2026-71573
Published
Aug 18, 2026
Updated
Aug 19, 2026
Vendor
Joomla
Product
Joomla! CMS
Classifications
CWE-93
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 19, 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=4.0.0-5.4.6
  2. Affected versionversion=6.0.0-6.1.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Joomla · Joomla! CMSversion=4.0.0-5.4.6; version=6.0.0-6.1.2

Published CVSS scores

6.9Joomla! ProjectCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:L

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-93Improper Neutralization of CRLF Sequences ('CRLF Injection')

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