Nextcloud Server prior to 20.0.0 stores passwords in a recoverable format even when external storage is not configured.
The storage of passwords in a recoverable format makes them subject to password reuse attacks by malicious users. In fact, it should be noted that recoverable encrypted passwords provide no significant benefit over plaintext passwords since they are subject not only to reuse by malicious attackers but also by malicious insiders. If a system administrator can recover a password directly, or use a brute force search on the available information, the administrator can use the password on other accounts.
The product does not require that users should have strong passwords, which makes it easier for attackers to compromise user accounts.
| Link | Tags |
|---|---|
| https://hackerone.com/reports/867164 | issue tracking exploit third party advisory |
| https://nextcloud.com/security/advisory/?id=NC-SA-2021-006 | vendor advisory |
| https://github.com/nextcloud/server/pull/21037 | third party advisory patch |
| https://github.com/nextcloud/server/issues/17439 | third party advisory exploit |
| https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L6BO6P6MP2MOWA6PZRXX32PLWPXN5O4S/ | vendor advisory |