8.1

CVE-2026-45281

Nextcloud: Cross-Account Calendar Takeover via Unauthorized Group-Member-Set Update

Cross-Account Calendar Takeover via Unauthorized Group-Member-Set Update

Nextcloud is an open source content collaboration platform. In Nextcloud Server from versions 32.0.0 to before 32.0.9, and 33.0.0 to before 33.0.3, with the knowledge of other users’ principal URL an attacker could possibly send a request to gain full access to their calendar. Therefore, the attacker must be an authenticated user. This is because of improper authorization controls in the backend of the calendar. If the attacker had access to the calendar, they would be able to view and modify it. It is recommended that the Nextcloud Server is upgraded to 33.0.3 or 32.0.9. It is recommended that the Nextcloud Enterprise Server is upgraded to 33.0.3, 32.0.9, 31.0.14.5, 30.0.17.9, 29.0.16.16, 28.0.14.17, 27.1.11.26, 26.0.13.26, 25.0.13.29, 24.0.12.34, 23.0.12.35, 22.2.10.39, or 21.0.9.23
Mögliche Gegenmaßnahme
Server: * If you cannot patch the system, please block access to the following endpoints as a temporary measure: * `remote.php/dav/principals/users/<userid>/calendar-proxy-read` * `remote.php/dav/principals/users/<userid>/calendar-proxy-write` * The relevant data is stored in the `oc_dav_cal_proxy` table. If you have doubts about the data integrity or need to reset the records, please clear this table. 
Enterprise Server: * If you cannot patch the system, please block access to the following endpoints as a temporary measure: * `remote.php/dav/principals/users/<userid>/calendar-proxy-read` * `remote.php/dav/principals/users/<userid>/calendar-proxy-write` * The relevant data is stored in the `oc_dav_cal_proxy` table. If you have doubts about the data integrity or need to reset the records, please clear this table. 
Daten sind bereitgestellt durch National Vulnerability Database (NVD)
Nextcloud ≫ Nextcloud Server SwEdition- Version >= 32.0.0 < 32.0.9
Nextcloud ≫ Nextcloud Server SwEdition- Version >= 33.0.0 < 33.0.3
Nextcloud ≫ Nextcloud Server SwEditionenterprise Version >= 21.0.0 < 21.0.9.23
Nextcloud ≫ Nextcloud Server SwEditionenterprise Version >= 22.0.0 < 22.2.10.39
Nextcloud ≫ Nextcloud Server SwEditionenterprise Version >= 23.0.0 < 23.0.12.35
Nextcloud ≫ Nextcloud Server SwEditionenterprise Version >= 24.0.0 < 24.0.12.34
Nextcloud ≫ Nextcloud Server SwEditionenterprise Version >= 25.0.0 < 25.0.13.29
Nextcloud ≫ Nextcloud Server SwEditionenterprise Version >= 26.0.0 < 26.0.13.26
Nextcloud ≫ Nextcloud Server SwEditionenterprise Version >= 27.0.0 < 27.1.11.26
Nextcloud ≫ Nextcloud Server SwEditionenterprise Version >= 28.0.0 < 28.0.14.17
Nextcloud ≫ Nextcloud Server SwEditionenterprise Version >= 29.0.0 < 29.0.16.16
Nextcloud ≫ Nextcloud Server SwEditionenterprise Version >= 30.0.0 < 30.0.17.9
Nextcloud ≫ Nextcloud Server SwEditionenterprise Version >= 31.0.0 < 31.0.14.5
Nextcloud ≫ Nextcloud Server SwEditionenterprise Version >= 32.0.0 < 32.0.9
Nextcloud ≫ Nextcloud Server SwEditionenterprise Version >= 33.0.0 < 33.0.3
VulnDex Vulnerability Enrichment
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Weitere Schwachstelleninformationen
SystemNextcloud
≫
Produkt Server
Version >= 32.0.0, < 32.0.9
Version >= 33.0.0, < 33.0.3
SystemNextcloud
≫
Produkt Enterprise Server
Version >= 21.0.0, < 21.0.9.23
Version >= 22.0.0, < 22.2.10.39
Version >= 23.0.0, < 23.0.12.35
Version >= 24.0.0, < 24.0.12.34
Version >= 25.0.0, < 25.0.13.29
Version >= 26.0.0, < 26.0.13.26
Version >= 27.0.0, < 27.1.11.26
Version >= 28.0.0, < 28.0.14.17
Version >= 29.0.0, < 29.0.16.16
Version >= 30.0.0, < 30.0.17.9
Version >= 31.0.0, < 31.0.14.5
Version >= 32.0.0, < 32.0.9
Version >= 33.0.0, < 33.0.3
Zu dieser CVE wurde keine Warnung gefunden.
EPSS Metriken
Typ Quelle Score Percentile
EPSS FIRST.org 0.28% 0.199
CVSS Metriken
Quelle Base Score Exploit Score Impact Score Vector String
security-advisories@github.com 8.1 2.8 5.2
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
CWE-639 Authorization Bypass Through User-Controlled Key

The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.

https://github.com/nextcloud/security-advisories/security/advisories/GHSA-hrrv-mp25-26vv
Vendor Advisory
Mitigation
https://github.com/nextcloud/server/pull/59962
Patch
Issue Tracking
https://hackerone.com/reports/3545964
Permissions Required
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-hrrv-mp25-26vv
Third Party Advisory