Skip to content

Calendar app allowed booking appointments without the generated token

Low
nickvergessen published GHSA-7x2j-2674-fj95 Dec 5, 2025

Package

Calendar (Nextcloud)

Affected versions

>= 4.0.0, >= 5.0.0, >= 6.0.0

Patched versions

4.7.19, 5.5.6, 6.0.1

Description

Impact

The calendar app allowed blindly booking appointments with a squential ID without known the appointment token.

Patches

It is recommended that Nextcloud Calendar is upgraded to 4.7.19, 5.5.6 or 6.0.1.

Workarounds

  • No workaround available

References

For more information

If you have any questions or comments about this advisory:

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

CVE ID

CVE-2025-66546

Weaknesses

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. Learn more on MITRE.