User Enumeration via Calendar Suggest in Nextcloud <5.5.17 & <6.2.3
CVE-2026-45286 Published on June 1, 2026
Nextcloud: Calendar app leaked user identifiers via attendee suggestion endpoint
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.
Vulnerability Analysis
CVE-2026-45286 is exploitable with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a small impact on confidentiality, a small impact on integrity and availability.
Weakness Type
What is an Information Disclosure Vulnerability?
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
CVE-2026-45286 has been classified to as an Information Disclosure vulnerability or weakness.
Affected Versions
nextcloud security-advisories:- Version >= 5.5.13, < 5.5.17 is affected.
- Version >= 6.2.0, < 6.2.3 is affected.