Re-Sharing allows increase of privileges (NC-SA-2020-029)
16th July 2020
Risk level: Low
CVSS v3 Base Score: 5.5 (AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:L)
HackerOne report: 889243
A logic error in Nextcloud Server 19.0.0 caused a privilege escalation allowing malicious users to reshare with higher permissions than they got assigned themselves.
- Nextcloud Server < 19.0.1 (CVE-2020-8223)
- Nextcloud Server < 18.0.7 (CVE-2020-8223)
- Nextcloud Server < 17.0.8 (CVE-2020-8223)
The error has been fixed.
It is recommended that the Nextcloud Server is upgraded to 19.0.1.
The Nextcloud team thanks the following people for their research and responsible disclosure of the above advisory:
- Dr. Alexander Fleischer - TU Ilmenau - Vulnerability discovery and disclosure.
This advisory is licensed CC BY-SA 4.0.