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

Status: published. Published: 2026-10-27. Updated: 2026-11-02.

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.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/Admidio/admidio/commit/5b0ee3585d2a69a6e85fee00b7b93f3ebc1e44d9

## Affected products and versions

- admidio / admidio (admidio/admidio): ≥ 0; < 5.0.17 (affected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 5.3 (medium); 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; source: CNA: VulnCheck

- CVSS 3.1: 4.3 (medium); CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N; source: CNA: VulnCheck

- CVSS 4.0: 5.3 (medium); 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/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; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 4.3 (medium); CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: 0.29% as of 2026-11-02; percentile 21.51%

- SSVC: exploitation poc; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-602

## Exploit evidence

- exploit: https://github.com/Admidio/admidio/security/advisories/GHSA-92g9-59rr-c3qg (ADP: CISA-ADP)

## References

- https://github.com/Admidio/admidio/issues/2231 (CNA: VulnCheck; issue-tracking)

- https://github.com/Admidio/admidio (CNA: VulnCheck; product)

- https://github.com/Admidio/admidio/security/advisories/GHSA-92g9-59rr-c3qg (CNA: VulnCheck; vendor-advisory)

- https://github.com/Admidio/admidio/commit/5b0ee3585d2a69a6e85fee00b7b93f3ebc1e44d9 (CNA: VulnCheck; patch)

- https://github.com/Admidio/admidio/releases/tag/v5.0.17 (CNA: VulnCheck; release-notes)

- https://github.com/Admidio/admidio/blob/v5.0.16/modules/events/events_function.php#L446-L462 (CNA: VulnCheck; technical-description)

- https://www.vulncheck.com/advisories/admidio-before-5.0.17-event-guest-restriction-bypass-via-events-function-php (CNA: VulnCheck; third-party-advisory)

- https://github.com/Admidio/admidio/security/advisories/GHSA-92g9-59rr-c3qg (ADP: CISA-ADP; exploit)

- https://github.com/Admidio/admidio (disclosure@vulncheck.com)

- https://github.com/Admidio/admidio/blob/v5.0.16/modules/events/events_function.php#L446-L462 (disclosure@vulncheck.com)

- https://github.com/Admidio/admidio/commit/5b0ee3585d2a69a6e85fee00b7b93f3ebc1e44d9 (disclosure@vulncheck.com)

- https://github.com/Admidio/admidio/issues/2231 (disclosure@vulncheck.com)

- https://github.com/Admidio/admidio/releases/tag/v5.0.17 (disclosure@vulncheck.com)

- https://github.com/Admidio/admidio/security/advisories/GHSA-92g9-59rr-c3qg (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/admidio-before-5.0.17-event-guest-restriction-bypass-via-events-function-php (disclosure@vulncheck.com)

- https://github.com/Admidio/admidio/security/advisories/GHSA-92g9-59rr-c3qg (134c704f-9b21-4f2e-91b3-4a467353bcc0)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-117554; retrieved 2026-11-02; source updated 2026-11-02

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-117554; retrieved 2026-11-02; source updated 2026-11-02

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-117554; retrieved 2026-11-02; source updated Not reported

Revision: 47babd69c92ef9c13c35777bcbd1ec543cbdedfc00d75f839f61b19ffc2a8628

Canonical: https://y2.dev/cve/CVE-2026-117554

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