CVE-2025-66511

MEDIUM4.8

Nextcloud Calendar app used predictable proposal participant tokens

Published Dec 5, 2025

Modified 2 months ago

Details

Nextcloud Calendar is a calendar app for Nextcloud. Prior to 6.0.3, the Calendar app generates participant tokens for meeting proposals using a hash function, allowing an attacker to compute valid participant tokens, which allowed them to request details and submit dates in meeting proposals. The tokens are not purely random generated. This vulnerability is fixed in 6.0.3.

References

WEB

https://github.com/nextcloud/calendar/commit/8de14ae87f321f5f09280d9895a27d54d24f33fb

WEB

https://github.com/nextcloud/calendar/pull/7659

WEB

https://github.com/nextcloud/security-advisories/security/advisories/GHSA-whm3-vv55-gf27

WEB

https://hackerone.com/reports/3385434

ADVISORY

https://www.cve.org/CVERecord?id=CVE-2025-66511

CVSS Analysis