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Downgrade encryption scheme and break integrity through known-plaintext attack (NC-SA-2020-039)

26th August 2020

Risk level: Low

CVSS v3 Base Score: 5.3 (AV:L/AC:H/PR:H/UI:N/S:C/C:N/I:H/A:N)

CWE: Cryptographic Issues - Generic (CWE-310)

HackerOne report: 742588


A cryptographic issue in Nextcloud Server 19.0.1 allowed an attacker to downgrade the encryption scheme and break the integrity of encrypted files.

Affected Software

  • Nextcloud Server < 19.0.2 (CVE-2020-8150)

Action Taken

The error has been fixed.


It is recommended that the Nextcloud Server is upgraded to 19.0.2.


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

This advisory is licensed CC BY-SA 4.0.

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