CVE-2025-66546

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 v3.1 Score

3.3

LOW

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

Weakness Type (CWE)

CWE-639 CWE-639

Affected Products

Vendor	Product	Versions
nextcloud	calendar	4.0.0 — 4.7.19
nextcloud	calendar	5.0.0 — 5.5.6
nextcloud	calendar	All
nextcloud	calendar	All
nextcloud	calendar	All
nextcloud	calendar	All
nextcloud	calendar	All
nextcloud	calendar	All
nextcloud	calendar	All

References

Advisories & Patches

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

Other References

https://github.com/nextcloud/calendar/pull/7537

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 3.3 (LOW).

How severe is CVE-2025-66546? +

CVE-2025-66546 has a CVSS v3.1 score of 3.3 out of 10, rated LOW. This is a low-severity vulnerability with limited impact.

What products are affected by CVE-2025-66546? +

CVE-2025-66546 affects products from nextcloud, specifically: calendar. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-66546? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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