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Joomla Event Manager EUVDEUVD-2026-66864

| CVE-2026-77990 MEDIUM
Authorization Bypass Through User-Controlled Key (CWE-639)
2026-08-27 security@joomla.org GHSA-839q-fphm-4fh3
5.3
CVSS 4.0 · Vendor: joomla
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Severity by source

Vendor (joomla) PRIMARY
5.3 MEDIUM
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
vuln.today AI
4.3 MEDIUM

Network-reachable IDOR requiring a valid Joomla login (PR:L) with read-only disclosure of attendee metadata; no scope change, integrity, or availability impact.

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

Primary rating from Vendor (joomla).

CVSS VectorVendor: joomla

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
X

Lifecycle Timeline

1
Analysis Generated
Aug 27, 2026 - 07:18 vuln.today

DescriptionCVE.org

Joomla Extension - joomlaeventmanager.net - Attendee lists readable by any logged-in user in Joomla Event Manager < 5.0.1 - A non-manager can therefore read attendee names, usernames, registration dates and statuses for events they do not manage, including lists belonging to unpublished events.

AnalysisAI

Broken object-level authorization in Joomla Event Manager before 5.0.1 allows any authenticated Joomla user to read attendee lists - including names, usernames, registration dates, and statuses - for events they do not manage. The exposure extends to unpublished events, meaning data intended to remain private before an event goes live is also accessible. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Obtain any valid Joomla account
Delivery
Authenticate and acquire session token
Exploit
Request attendee list endpoint with target event ID
Execution
Enumerate event IDs to expand access
Persist
Exfiltrate attendee names, usernames, and statuses
Impact
Access unpublished event attendee data

Vulnerability AssessmentAI

Exploitation Exploitation requires at minimum a valid, active Joomla session at the lowest authenticated privilege tier (e.g., Registered or Subscriber role) - unauthenticated anonymous visitors cannot exploit this flaw. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 4.0 score of 5.3 and associated vector correctly reflect a medium-severity, low-complexity, read-only confidentiality flaw requiring only a valid Joomla login. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An authenticated Joomla user with a standard Registered-level account navigates to or directly requests the attendee list endpoint for an event they have no management rights over, supplying the event's identifier in the request. By iterating through sequential or enumerable event IDs, the attacker can systematically harvest attendee names, usernames, registration dates, and statuses across all events on the site, including those not yet published. …
Remediation Upgrade Joomla Event Manager to version 5.0.1 or later, as confirmed by the CVE description as the fixed release. … Detailed patch versions, workarounds, and compensating controls in full report.

Threat intelligence, references, and detailed analysis are available after sign-in.

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EUVD-2026-66864 vulnerability details – vuln.today

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