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)
CWE: Improper Privilege Management (CWE-269)
HackerOne report: 889243
Description
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.
Affected Software
- Nextcloud Server < 19.0.1 (CVE-2020-8223)
- Nextcloud Server < 18.0.7 (CVE-2020-8223)
- Nextcloud Server < 17.0.8 (CVE-2020-8223)
Action Taken
The error has been fixed.
Resolution
It is recommended that the Nextcloud Server is upgraded to 19.0.1.
Acknowledgements
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.