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Joomla CMS CVE-2026-90917

| EUVDEUVD-2026-89076 MEDIUM
Improper Access Control (CWE-284)
2026-09-29 Joomla GHSA-4xw6-jw26-gp2r
6.9
CVSS 4.0 · Vendor: Joomla
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Access public Joomla tag/tagged-item output
  2. Exploit
    Request items filtered by tag
  3. Execution
    ACL check omitted on tagged output
  4. Impact
    View content from inaccessible categories

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Access control enforcement
MITRE ATT&CK

1 technique across 1 tactic: Defense Evasion

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Exploitation Conditions

Requires the Joomla site to expose tagged-item output (tag views, tag-based listings or the tagged-items module) where tagged content spans categories with differing access levels - the bug is that the ACL/category access check is not applied to these tagged outputs. Exploitation needs NO authentication and NO user interaction (PR:N/UI:N), so any anonymous visitor can trigger it against a default install running an affected version (4.0.0-5.4.8 or 6.0.0-6.1.3). The limiting factor is impact scope: only content items that have been tagged and placed in access-restricted categories are exposed, and only their content is disclosed (confidentiality-only, no modification or DoS).

Impact

This is a genuine but low-to-moderate priority issue. The vendor CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N) scoring 6.9 signals a remotely reachable, unauthenticated, low-complexity flaw - but crucially the impact is confidentiality-only and rated LOW, with no integrity or availability effect and no scope change. So despite the 'medium' numeric score, this is an information-disclosure ACL bypass, not a system compromise. No EPSS score, no CISA KEV listing, and no public POC were provided, meaning there is no evidence of exploitation activity - status is 'no public exploit identified at time of analysis.' The most notable signal is PR:N: unlike its self-reported sibling Joomla ACL advisories from the same September 2026 batch (CVE-2026-92223/92225/92232/92222, all PR:H authenticated), this flaw requires NO authentication, which meaningfully broadens who can exploit it. The CWE-284 (improper access control) classification is consistent with the description; note the 'Authentication Bypass' tag is loose - this is authorization bypass / info disclosure, not credential/authentication bypass. Net: a real, broadly-deployed-product issue worth patching, but the low confidentiality-only impact keeps it below the memory-corruption/RCE tier.

Exploit ScenarioDerived

An unauthenticated visitor to a Joomla site browses tagged-item listings (e.g. a tag view or tagged-content module) and receives content items that belong to categories their access level should hide, such as registered-only or restricted articles. Because no login is required and complexity is low, this can be probed directly against default configurations. No public exploit code is available at time of analysis.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
No patch listed yet 0.3% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 29, 2026

Improper access-control checks in Joomla's tagged-item output let unauthenticated visitors read content items that belong to access-restricted categories, exposing only article content (confidentiality-only) with no modification or denial-of-service impact. Affected releases are Joomla! CMS 4.0.0 through 5.4.8 and 6.0.0 through 6.1.3; exploitation requires no authentication and no user interaction (PR:N/UI:N in both the supplied CVSS 4.0 vector and our assessed CVSS 3.1 vector), so any anonymous visitor can trigger it on a default site that renders tagged items where tags span categories with differing view levels. No public exploit code was identified at time of analysis and the issue is not confirmed as actively exploited; the practical risk is bounded because disclosure is limited to tagged items in restricted categories, which is why our independent assessment treats this as a genuine but low-to-moderate priority issue.

RemediationAI

Patch status must be taken from the vendor advisory: the supplied data does not state an exact fixed version, so consult the Joomla Security Centre advisory 20260907 (https://developer.joomla.org/security-centre/1087-20260907-core-improper-acl-checks-in-outputs-for-tagged-items.html) and apply the corrected Joomla! CMS release it identifies for the 4.x/5.x and 6.x branches, then re-check that the installed version has moved past the affected windows (4.0.0-5.4.8 and 6.0.0-6.1.3). If immediate patching is not possible, the most effective compensating control is to stop exposing tag-based output: unpublish or disable the "tagged items" module and any menu item or template override that renders com_tags list/layout output, accepting the trade-off that tag navigation, tag clouds, and tag-based SEO landing pages will disappear or 404. Alternatively, audit which categories use restricted Access Levels and remove tags from the articles inside them, or set those tags to unpublished, with the trade-off that editors lose tagging metadata for that content and tag associations must be restored after patching. Once tagged output is re-enabled or the site is patched, review web logs for requests to com_tags/tag view endpoints carrying unusual tag IDs as a retroactive indicator of content enumeration; note that no authentication is required, so IP-based blocking, rate limiting, or WAF rules are only weak friction rather than a real fix and cannot distinguish legitimate tag browsing from enumeration.

Affected VersionsENISA

Joomla! CMS 6.0.0-6.1.3
Joomla! CMS 4.0.0-5.4.8

Affected Packages

euvd joomla_cms no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

The flaw is rooted in CWE-284 (Improper Access Control) and sits in Joomla's tagging subsystem, i.e. the com_tags component and the "tagged items" module/layouts that aggregate articles by their assigned tags. Joomla enforces content visibility through Access Levels (viewing access levels applied to categories and articles), and core components are expected to re-apply that category-level ACL check whenever they render items pulled out of context. In the vulnerable versions the tagged-item output paths resolve and render articles without re-checking the access level of the category each article belongs to, so content that would be hidden on a normal category or article view is exposed through the tag-based listing. The supplied CPE cpe:2.3:a:joomla!_project:joomla!_cms:*:*:*:*:*:*:*:* is version-agnostic, so it identifies the Joomla! CMS product family rather than a precise build; the authoritative affected windows come from the advisory text (4.0.0-5.4.8 and 6.0.0-6.1.3). The CVSS 4.0 vector supplied by the vendor (AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N) describes a network-reachable, unauthenticated, no-interaction bug with low confidentiality impact and no subsequent-system impact; our independent CVSS 3.1 assessment (AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N) agrees on the attack prerequisites and on impact being confined to information disclosure.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (Joomla) PRIMARY 6.9 MEDIUM
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
vuln.today AI 5.3 MEDIUM

Unauthenticated network access with no interaction (PR:N/UI:N) but only low-severity read exposure of restricted tagged content, so C:L and I/A:N.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (Joomla).

CVSS VectorVendor: Joomla

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Vulnerable system: Confidentiality
Low
Vulnerable system: Integrity
None
Vulnerable system: Availability
None
Subsequent system: Confidentiality
None
Subsequent system: Integrity
None
Subsequent system: Availability
None

DescriptionCVE.org

Joomla! Core - [20260907] - Core - Improper ACL checks in outputs for tagged items in Joomla 4.0.0-5.4.8, 6.0.0-6.1.3 - An improper access check allows unauthorized users to view content items from inaccessible categories.

Threat Intelligence Overview

EPSS Score
0.3%
Top 82% exploitable
Prevalence
Ubiquitous
Joomla is one of the most widely deployed open-source PHP CMS platforms
Data Quality
5 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.3%
Patch available No
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
Yes
Human Impact· derived
High
Technical Impact
Partial

Priority Score

34
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +34
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

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