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.

Scores

EPSS (exploitation in 30 days)

0.28% · top 79% of all CVEs (6 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 4.3.

Weakness

• CWE-200: Exposure of Sensitive Information to an Unauthorized Actor (opens in a new tab)All about CWE-200 and its CVEs

Affected products

• nextcloud · security-advisories

  • affected >= 5.5.13, < 5.5.17
  • affected >= 6.2.0, < 6.2.3

References (4)

• https://github.com/nextcloud/security-advisories/security/advisories/GHSA-r697-74m9-gvf2 (opens in a new tab)x_refsource_CONFIRM
• https://github.com/nextcloud/calendar/issues/7971 (opens in a new tab)x_refsource_MISC
• https://github.com/nextcloud/calendar/pull/8197 (opens in a new tab)x_refsource_MISC
• https://hackerone.com/reports/3540663 (opens in a new tab)x_refsource_MISC

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-45286](https://trackcve.app/badge/CVE-2026-45286.svg)](https://trackcve.app/cve/CVE-2026-45286)

Record last updated 1 Jun 2026, 19:13 UTC.