CVE-2023-48304: Nextcloud Server vulnerable to attacker enabling/disabling birthday calendar for any user

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2023-11-21 · updated 2026-06-17
Weakness: CWE-639

Description

Nextcloud Server provides data storage for Nextcloud, an open source cloud platform. Starting in version 25.0.0 and prior to versions 25.0.11, 26.0.6, and 27.1.0 of Nextcloud Server and starting in version 22.0.0 and prior to versions 22.2.10.16, 23.0.12.11, 24.0.12.7, 25.0.11, 26.0.6, and 27.1.0 of Nextcloud Enterprise Server, an attacker could enable and disable the birthday calendar for any user on the same server. Nextcloud Server 25.0.11, 26.0.6, and 27.1.0 and Nextcloud Enterprise Server 22.2.10.16, 23.0.12.11, 24.0.12.7, 25.0.11, 26.0.6, and 27.1.0 contain patches for this issue. No known workarounds are available.

Affected products

Nextcloud Server: from 22.0.0 through 22.2.10.16; from 23.0.0 before 23.0.12.11; from 24.0.0 before 24.0.12.7; from 25.0.0 before 25.0.11; from 26.0.0 before 26.0.6; from 27.0.0 before 27.1.0 — fixed in 23.0.12.11, 24.0.12.7, 25.0.11, 26.0.6, 27.1.0

How to fix

Upgrade to a fixed version: Nextcloud Server 23.0.12.11, 24.0.12.7, 25.0.11, 26.0.6. Check the vendor advisory for mitigations.

References

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