---
id: CVE-2026-45286
title: Nextcloud is an open source content collaboration platform
summary: >-
  Nextcloud is an open source content collaboration platform. From versions
  5.5.13 to before 5.5.17, and 6.2.0 to before 6.2.3, an authenticated user can
  enumerate users on the same Nextcloud instance by using the Calendar app's
  endpoint f…
severity: medium
cvss: 4.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N'
cwe:
  - CWE-200
vendor: nextcloud
product: calendar
affected:
  - 'calendar >= 5.5.13, < 5.5.17'
  - 'calendar >= 6.2.0, < 6.2.3'
patched:
  - calendar 6.2.3
published: '2026-06-01'
updated: '2026-07-22'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-45286'
references:
  - url: 'https://github.com/nextcloud/calendar/issues/7971'
    label: security-advisories@github.com
  - url: 'https://github.com/nextcloud/calendar/pull/8197'
    label: security-advisories@github.com
  - url: >-
      https://github.com/nextcloud/security-advisories/security/advisories/GHSA-r697-74m9-gvf2
    label: security-advisories@github.com
  - url: 'https://hackerone.com/reports/3540663'
    label: security-advisories@github.com
tags:
  - nvd
epss: 0.00281
epssPercentile: 0.20824
ingestedAt: '2026-07-23T07:14:46.429Z'
---

## Overview

Nextcloud is an open source content collaboration platform. From versions 5.5.13 to before 5.5.17, and 6.2.0 to before 6.2.3, an authenticated user can enumerate users on the same Nextcloud instance by using the Calendar app's endpoint for suggesting attendees. The sharing restrictions, applied to other endpoints, were not effective here. This issue has been patched in versions 5.5.17 and 6.2.3.

## Affected

- `calendar >= 5.5.13, < 5.5.17`
- `calendar >= 6.2.0, < 6.2.3`

## Remediation

Upgrade past the affected range:

- `calendar 6.2.3`