Is CVE-2025-66546 in the CISA KEV catalog?

No. CVE-2025-66546 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2025-66546?

CVE-2025-66546 has a CVSS v3 base score of 3.3 (LOW).

What is the EPSS score for CVE-2025-66546?

CVE-2025-66546 has an EPSS score of 0.12% (2th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2025-66546?

Upgrade calendar to 5.5.6 or later.

CVE & CISA-KEV Catalog

CVE-2025-66546

LOW

3.3

CVSS v3

NVD

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.

CWE-639Authorization Bypass Through User-Controlled Key

How to fix

Remediation Available

calendarNVD

Affected:>= 5.0.0, < 5.5.6Fixed in:5.5.6CVE-2025-66546derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorLocal

Attack ComplexityLow

Privileges RequiredLow

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityLow

IntegrityNone

AvailabilityNone

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

Exploit Intelligence

0.12%probability of exploitation in 30 days

2ndpercentile

Low risk: more likely to be exploited than 2% of all known CVEs.

References

Patch2

Vendor Advisory1

hackerone.com

Issue Tracking1

github.com

Related Vulnerabilities

Other CWE-639 (Authorization Bypass Through User-Controlled Key) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2023-6875	Critical	9.8	90%	-	-
CVE-2024-46982	High	7.5	61%	-	Fix
CVE-2021-45428	Critical	9.8	57%	-	-
CVE-2019-17382	Critical	9.1	54%	-	Fix
CVE-2019-13360	Critical	9.8	24%	-	-
CVE-2023-48783	Medium	5.4	22%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-12-09.