CVE-2025-66550

mediumpriority · track · 0EPSS 0.003 · 27 %ileDEEURUUS

grimoire priorityP3 · Track

Exploitable?

—

no known exploitation

Likely / severe?

0.34% (27th) EPSS

CVSS 5.7 · medium

Is it mine?

16 products

Check your exposure

Who says so?

5 sources

cnnvd · enisa_euvd · fstec_bdu · cert_bund

EPSS · scored 2026-10-27

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

Technical severity, 0–10. One row per scoring source.

5.7

010

base score 0–10 · higher = more severe · hover a vector to decode

v3.15.7mediumAV:N/AC:L/PR:L/UI:R/S:U/C:N/I:H/A:Nsecondary · FSTEC (BDU) RU

v3.15.7mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:H/A:Nsecondary · ENISA EU

v3.15.7mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:H/A:Nsecondary · security-advisories@github.comexploitability 2.1 · impact 3.6

v3.15.2mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:H/A:N/E:Usecondary · CVSS-BT (t0sche)

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Trackcoordinatorcisa_ssvcUS

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-241USCWE-241US

affected products (16)

Products and version ranges known to be affected.

Nextcloud Nextcloud Approvalall versionscert_bundDEcpe:/a:nextcloud:nextcloud:approval
Nextcloud Nextcloud Calendarall versionscert_bundDEcpe:/a:nextcloud:nextcloud:calendar
Nextcloud Nextcloud Deckall versionscert_bundDEcpe:/a:nextcloud:nextcloud:deck
Nextcloud Nextcloud Desktopall versionscert_bundDEcpe:/a:nextcloud:nextcloud:desktop
Nextcloud Nextcloud Enterprise Serverall versionscert_bundDEcpe:/a:nextcloud:nextcloud:enterprise_server
Nextcloud Nextcloud Groupfoldersall versionscert_bundDEcpe:/a:nextcloud:nextcloud:groupfolders
Nextcloud Nextcloud Mailall versionscert_bundDEcpe:/a:nextcloud:nextcloud:mail
Nextcloud Nextcloud Serverall versionscert_bundDEcpe:/a:nextcloud:nextcloud:server
Nextcloud Nextcloud Tablesall versionscert_bundDEcpe:/a:nextcloud:nextcloud:tables
nextcloud security-advisories≤ < 4.7.17enisa_euvdEU
nextcloud security-advisories5.0.0-rc.1, → 5.2.4enisa_euvdEU
Nextcloud GmbH Nextcloud Calendar≤ 5.2.4fstec_bduRU
Nextcloud GmbH Nextcloud Calendar≤ 4.7.17fstec_bduRU
ООО «Ред Софт» РЕД ОС≤ 8.0fstec_bduRU
nextcloud calendar4.0.0 → 4.7.17nvdUScpe:2.3:a:nextcloud:calendar:*:*:*:*:*:*:*:*
nextcloud calendar5.0.0 → 5.2.4nvdUScpe:2.3:a:nextcloud:calendar:*:*:*:*:*:*:*:*

advisories (1)

Vendor and ecosystem advisories describing this.

WID-SEC-W-2025-2752Nextcloud: Mehrere SchwachstellenDeutsch2025-12-04csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in Nextcloud ausnutzen, um Dateien zu manipulieren, um Informationen offenzulegen, um einen Cross-Site Scripting Angriff durchzuführen, um Sicherheitsvorkehrungen zu umgehen, und um falsche Informationen darzustellen.

also known as (3)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd fstec_bdu cert_bund nvd NVD CVE.org MITRE

published 2025-12-05modified 2026-10-18

references (13)

External citations — patches, advisories, analysis.

scry

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