Vulnerability Report

CVE-2025-66546

Title: Blindly booking appointments with sequential ID without token in Nextcloud Calendar

Auth Bypass

Proof Of Concept

No public PoC currently indexed for CVE-2025-66546.

CWE Category CWE-639

Published Date Dec 05, 2025

Modified Date Dec 09, 2025

Exploit Status Not Found

Score 3.3 CVSS v3.1

Exploit Probability (EPSS)

0.01%

Vulnerability Summary

CVE-2025-66546: Nextcloud Calendar is a calendar app for Nextcloud. Prior to 4.7.19, 5.5.6, and 6.0.1, the calendar app allowed blindly booking appointments with a squential ID without known the appointment token. This vulnerability is fixed in 4.7.19, 5.5.6, and 6.0.1.

Impacted Vendors

karen_stevenson 1

nextcloud 1

Reference Links

https://github.com/nextcloud/calendar/commit/f41650c3681fc4a4130eb883f5c0899c011326b3 https://github.com/nextcloud/calendar/pull/7537 https://github.com/nextcloud/security-advisories/security/advisories/GHSA-7x2j-2674-fj95 https://hackerone.com/reports/3275810

CVSS v3.1

Source Entity [email protected]

Severity LOW

3.3

Attack Vector

LOCAL

Complexity

LOW

Privileges

N/A

Interaction

NONE

Confidentiality

N/A

Integrity

N/A

Availability

N/A

Scope

UNCHANGED

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

Associated Attack Patterns (CAPEC)

Total: Patterns

CVE-2025-66546 Exploits & PoCs (Proof Of Concept)

No public PoCs found in our database for this CVE.

December 09, 2025 MODIFIED

Vulnerability data or affected products updated.

December 09, 2025 MODIFIED

Vulnerability data updated via NVD.

December 05, 2025 PUBLISHED

Vulnerability first announced in NVD.

Attack Vector Matrix

Access Vector LOCAL

Complexity LOW

Privileges N/A

Interaction NONE

CVSS Vector String


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

Affected Stack

No specific products linked.