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TI-2023-24171 Aliases CVE-2023-45150

Inviting excessive long email addresses to a calendar event makes the Nextcloud server unresponsive

Priority MEDIUM 53CWE-400Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · Low
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-400.

Summary

Nextcloud calendar is a calendar app for the Nextcloud server platform. Due to missing precondition checks the server was trying to validate strings of any length as email addresses even when megabytes of data were provided, eventually making the server busy and unresponsive. It is recommended that the Nextcloud Calendar app is upgraded to 4.4.4. The only workaround for users unable to upgrade is to disable the calendar app.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00477 41st percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed security-advisories (nextcloud): 4.4.4

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
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-advisories1.0.0 to before 4.4.44.4.4Patch availableCNA
  • security-advisories Vendornextcloud Affected 1.0.0 to before 4.4.4 Fixed in 4.4.4 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:nextcloud:calendar:*:*:*:*:*:*:*:*1.0 to before 4.4.4Vulnerablenextcloud
  • cpe:2.3:a:nextcloud:calendar:*:*:*:*:*:*:*:* Versions 1.0 to before 4.4.4 Vulnerable ·nextcloud

Remediation

  • Fix · CNA security-advisories (nextcloud) Fixed in 4.4.4

Timeline

  1. 2026-10-02 Threatist record created from CVE-2023-45150

References

Exploit 1

Patch 1

Advisory 1

  • TI-2022-08650 Command Injection in Appointment Emails for Nextcloud Calendar CVSS 3.1CRITICAL 9.8
  • 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
  • TI-2024-24828 Nextcloud Calendar's event create can create attachments that link to other websites CVSS 3.1MEDIUM 4.6
See all 9 →

Sources

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