Impact

There was a lack of ratelimiting on the public share link mount endpoint. This may have allowed an attacker to enumerate potentially valid share tokens.

Patches

It is recommended that the Nextcloud Server is upgraded to 19.0.13, 20.0.11 or 21.0.3

Workarounds

None.

References

• HackerOne
• Pull Request

For more information

If you have any questions or comments about this advisory:

• Create a post in nextcloud/security-advisories
• Customers: Open a support ticket at support.nextcloud.com