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TI-2026-33086 Aliases CVE-2026-45286

Nextcloud: Calendar app leaked user identifiers via attendee suggestion endpoint

Priority LOW 20CWE-200Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
Information disclosure
Confidentiality · integrity · availability
Low · None · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-200.

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 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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00281 20th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed security-advisories (nextcloud): 5.5.17, 6.2.3

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
nextcloudsecurity-advisories5.5.13 to before 5.5.17; 6.2.0 to before 6.2.35.5.17, 6.2.3Patch availableCNA
  • security-advisories Vendornextcloud Affected 5.5.13 to before 5.5.17; 6.2.0 to before 6.2.3 Fixed in 5.5.17, 6.2.3 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:nextcloud:calendar:*:*:*:*:*:*:*:*5.5.13 to before 5.5.17; 6.2.0 to before 6.2.3Vulnerablenextcloud
  • cpe:2.3:a:nextcloud:calendar:*:*:*:*:*:*:*:* Versions 5.5.13 to before 5.5.17; 6.2.0 to before 6.2.3 Vulnerable ·nextcloud

Remediation

  • Fix · CNA security-advisories (nextcloud) Fixed in 5.5.17, 6.2.3

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-45286

References

Exploit 1

Patch 1

Advisory 1

Other 1

  • TI-2022-08650 Command Injection in Appointment Emails for Nextcloud Calendar CVSS 3.1CRITICAL 9.8
  • TI-2023-24171 Inviting excessive long email addresses to a calendar event makes the Nextcloud server unresponsive CVSS 3.1MEDIUM 4.3
  • TI-2023-26171 Calendar app returns full stacktrace when an error happens while editing appointment CVSS 3.1MEDIUM 6.5
  • TI-2025-40933 Nextcloud Calendar app used predictable proposal participant tokens CVSS 3.1MEDIUM 6.5
  • TI-2025-40961 Nextcloud Calendar attachments of local files are offered to downloaded CVSS 3.1MEDIUM 5.7
  • TI-2018-02759 Cross-site scripting in Nextcloud Calendar application CVSS 3.1MEDIUM 4.8
See all 9 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences