5.7

CVE-2025-66550: nextcloud calendar

CVSS: 5.7v3.1MediumAnalyzed
Published 05-12-2025Last modified 05-12-2025
Open JSON

Vulnerability summary

CVE-2025-66550 is a medium (CVSS 5.7) vulnerability in nextcloud calendar. EPSS estimates a 0.34% chance of exploitation in the next 30 days, higher than 26.1% of scored vulnerabilities.

Overall risk
23/100
0100
Low · default modelHow is this calculated?
CVSS score
5.7/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.34%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 05-12-2025
    PublishedVulnerability first disclosed.
  2. 05-12-2025
    Last modifiedVulnerability information updated.

Description

Nextcloud Calendar is a calendar app for Nextcloud. Prior to 4.7.17 and 5.2.4, when a malicious user creates a calendar event with a crafted attachment that links to a download link of a file on the same Nextcloud server, the file would be downloaded without the user confirming the action. This vulnerability is fixed in 4.7.17 and 5.2.4.

CVSS metrics

2 scores · 2 sources · 1 version

EPSS trend

Probability

0.34%

Chance of exploitation in the next 30 days

Percentile

26%

Versus all other CVEs

30-day change

0.00 pp

From 0.34% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.34%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Nextcloud2 products

1 vendor · 2 products

References

4 links