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PatchSiren cyber security CVE debrief

CVE-2026-48904 Joomla! Project CVE debrief

A privilege escalation vulnerability exists in Joomla's com_users component, specifically within the group editing webservice endpoint. The improper access check allows unauthenticated or lower-privileged actors to escalate privileges by manipulating group assignments through the webservice API. The vulnerability affects Joomla 4.0.0 through 5.4.5 and 6.0.0 through 6.1.0. The CVSS 4.0 vector indicates network attack vector with low attack complexity, requiring no privileges or user interaction, with high impact to integrity. The vendor has released security advisory 20260514 addressing this issue. Organizations should prioritize patching to versions 5.4.6 or 6.1.1 or later, and review webservice access controls as interim mitigation.

Vendor
Joomla! Project
Product
Joomla! CMS
CVSS
HIGH 8.2
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-26
Original CVE updated
2026-05-26
Advisory published
2026-05-26
Advisory updated
2026-05-26

Who should care

Joomla site administrators, security teams managing content management systems, organizations using Joomla's webservice API for user management integrations, and compliance officers responsible for access control audits in CMS environments

Technical summary

The vulnerability stems from insufficient access validation in the group editing functionality exposed through Joomla's webservice API. The com_users component fails to properly verify that the requesting principal has authorization to modify user group memberships. This allows attackers to send crafted API requests to escalate privileges by adding users to administrative groups. The attack is network-accessible with low complexity and requires no authentication or user interaction in the default configuration. The integrity impact is rated HIGH per CVSS 4.0, though confidentiality and availability impacts are not directly affected. The vulnerability spans multiple major versions, indicating a systemic access control weakness in the webservice implementation rather than a regression in specific code changes.

Defensive priority

HIGH

Recommended defensive actions

  • Upgrade Joomla installations to version 5.4.6 or 6.1.1 or later immediately
  • If immediate patching is not feasible, restrict access to the com_users webservice endpoints to trusted administrative IP ranges
  • Review user group assignments for unauthorized changes made since 2026-05-14
  • Enable comprehensive logging on webservice endpoints to detect anomalous group modification requests
  • Verify no unauthorized accounts have been granted elevated privileges through the affected endpoint

Evidence notes

Vendor advisory confirms improper access control in com_users webservice endpoints. CPE data specifies affected version ranges. CVSS 4.0 scoring from NVD with integrity impact.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-48904 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-48904

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-48904 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-48904

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.