CVE-2026-45286
Nextcloud: Calendar app leaked user identifiers via attendee suggestion endpoint
Description
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.
INFO
Published Date :
June 1, 2026, 7:16 p.m.
Last Modified :
June 3, 2026, 8:35 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update Nextcloud to version 5.5.17 or later.
- Update Nextcloud to version 6.2.3 or later.
- Restrict access to the Calendar app's attendee suggestion endpoint.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-45286.
| URL | Resource |
|---|---|
| https://github.com/nextcloud/calendar/issues/7971 | Exploit Issue Tracking Patch |
| https://github.com/nextcloud/calendar/pull/8197 | Issue Tracking Patch |
| https://github.com/nextcloud/security-advisories/security/advisories/GHSA-r697-74m9-gvf2 | Mitigation Vendor Advisory |
| https://hackerone.com/reports/3540663 | Permissions Required |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-45286 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-45286
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-45286 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-45286 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Jun. 03, 2026
Action Type Old Value New Value Added CWE NVD-CWE-noinfo Added CPE Configuration OR *cpe:2.3:a:nextcloud:calendar:*:*:*:*:*:*:*:* versions from (including) 5.5.13 up to (excluding) 5.5.17 *cpe:2.3:a:nextcloud:calendar:*:*:*:*:*:*:*:* versions from (including) 6.2.0 up to (excluding) 6.2.3 Added Reference Type GitHub, Inc.: https://github.com/nextcloud/calendar/issues/7971 Types: Exploit, Issue Tracking, Patch Added Reference Type GitHub, Inc.: https://github.com/nextcloud/calendar/pull/8197 Types: Issue Tracking, Patch Added Reference Type GitHub, Inc.: https://github.com/nextcloud/security-advisories/security/advisories/GHSA-r697-74m9-gvf2 Types: Mitigation, Vendor Advisory Added Reference Type GitHub, Inc.: https://hackerone.com/reports/3540663 Types: Permissions Required -
New CVE Received by [email protected]
Jun. 01, 2026
Action Type Old Value New Value Added Description 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. Added CVSS V3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N Added CWE CWE-200 Added Reference https://github.com/nextcloud/calendar/issues/7971 Added Reference https://github.com/nextcloud/calendar/pull/8197 Added Reference https://github.com/nextcloud/security-advisories/security/advisories/GHSA-r697-74m9-gvf2 Added Reference https://hackerone.com/reports/3540663