Nextcloud: Cross-Account Calendar Takeover via Unauthorized Group-Member-Set Update_CVE-2026-45281

8.1 / 10

HIGH

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Description

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

Basic Information

ID CVE-2026-45281

Source GitHub_M

Published Jun 1, 2026 at 16:52

Affected Product

Vendor nextcloud

Product security-advisories

Version >= 32.0.0, < 32.0.9

Affected Versions nextcloud security-advisories >= 32.0.0, < 32.0.9
nextcloud security-advisories >= 33.0.0, < 33.0.3

CWE Classification

CWE-639

References

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    "published": "2026-06-01T16:52:57.245Z",
    "modified": "2026-06-01T16:52:57.245Z",
    "type": "cve",
    "title": "Nextcloud: Cross-Account Calendar Takeover via Unauthorized Group-Member-Set Update",
    "source": "GitHub_M",
    "references": "https://github.com/nextcloud/security-advisories/security/advisories/GHSA-hrrv-mp25-26vv\nhttps://github.com/nextcloud/server/pull/59962\nhttps://hackerone.com/reports/3545964",
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