---
id: "CVE-2026-117554"
kind: "vulnerability"
aliases: ["CVE-2026-117554"]
title: "Admidio: members can fill event seats by submitting guest field"
severity: "medium"
cvss: 5.3
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["admidio", "package", "php", "self-hosted"]
not_affected_if: ["admidio-5.0.17-or-later", "events-module-unused"]
published_at: "2026-10-27T14:16:35+00:00"
first_seen_at: "2026-10-27T14:32:18+00:00"
updated_at: "2026-10-27T14:33:12+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-117554", "first_seen_at": "2026-10-27T14:32:18+00:00"}]
---

# Admidio: members can fill event seats by submitting guest field

Admidio before 5.0.17 lets an authenticated member register event guests even when guests are disallowed, by sending the additional_guests field. An attacker can set that field to the remaining seat count and block other members from registering for the event.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed Admidio version (`5.0.17` or later is fixed).
- Look for the guest handling in `modules/events/events_function.php` in the installed code.

## Fix

- Upgrade Admidio to `5.0.17` or later.

## Timeline

- 2026-10-27T14:32:18+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-117554

## From the sources

Admidio before 5.0.17 contains an improper access control vulnerability that allows authenticated members to register event guests by submitting the additional_guests field when guests are disallowed. Attackers can set additional_guests to the remaining seat count in modules/events/events_function.php to exhaust event capacity and block other members from registering.

---

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