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Increase random used for encryption (NC-SA-2020-023)

4th June 2020

Risk level: Low

CVSS v3 Base Score: 2.2 (AV:N/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:N)

CWE: Cryptographic Issues - Generic (CWE-310)

HackerOne report: 852841


A too small set of random characters being used for encryption in Nextcloud Server 18.0.4 allowed decryption in shorter time than intended.

Affected Software

  • Nextcloud Server < 19.0.0 (CVE-2020-8173)
  • Nextcloud Server < 18.0.5 (CVE-2020-8173)
  • Nextcloud Server < 17.0.7 (CVE-2020-8173)

Action Taken

The error has been fixed.


It is recommended that the Nextcloud Server is upgraded to 19.0.0.


The Nextcloud team thanks the following people for their research and responsible disclosure of the above advisory:

  • Lynn Stephenson - Vulnerability discovery and disclosure.

This advisory is licensed CC BY-SA 4.0.

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