Low severity · published Dec 5, 2025
CVE-2025-66546
Nextcloud Calendar app allowed booking appointments without the generated token
3.3
CVSS
0.1%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
Low
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.1% · higher than 3% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
SE
security-advisories · nextcloud
>= 6.0.0-rc.1, < 6.0.1; >= 5.0.0-rc.1, < 5.5.6; >= 3.0.0-beta1, < 4.7.19 · source: vendor
CA
Calendar · Nextcloud
4.0.0 before 4.7.19; 5.0.0 before 5.5.6; 6.0.0; 6.0.0; 6.0.0; 6.0.0; +3 more · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-66546
CVE.org
https://www.cve.org/CVERecord?id=CVE-2025-66546
Patch
https://github.com/nextcloud/calendar/commit/f41650c3681fc4a4130eb883f5c0899c011326b3
Issue Tracking
https://github.com/nextcloud/calendar/pull/7537
Patch
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-7x2j-2674-fj95
Issue Tracking
https://hackerone.com/reports/3275810
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