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CVE-2025-66546Nextcloud Calendar app allowed booking appointments without the generated token
- 3.3LowCVSS base score
- 0.15%Exploitation in 30 daysEPSS · top 96% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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.
Timeline
ID reserved
By GitHub_M
- 1 day later
· 1 day later
Published
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | Low3.3 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N |
| NVDNVD · Analyzed | 3.1 | Low3.3 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N |
- EPSS (exploitation in 30 days)
- 0.15% · top 96% of all CVEs (14 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
Loading the EPSS history…
The list uses the assigner's score when there is one, then CISA's, then NVD's: Low 3.3.
Affected products
nextcloud · security-advisories
- affected >= 6.0.0-rc.1, < 6.0.1
- affected >= 5.0.0-rc.1, < 5.5.6
- affected >= 3.0.0-beta1, < 4.7.19
References
References4
- https://github.com/nextcloud/security-advisories/security/advisories/GHSA-7x2j-2674-fj95 (opens in a new tab)x_refsource_CONFIRM
- https://github.com/nextcloud/calendar/pull/7537 (opens in a new tab)x_refsource_MISC
- https://github.com/nextcloud/calendar/commit/f41650c3681fc4a4130eb883f5c0899c011326b3 (opens in a new tab)x_refsource_MISC
- https://hackerone.com/reports/3275810 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2025-201445 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
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[](https://cveledger.app/cve/CVE-2025-66546)Record last updated .