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Potential DDoS when posting long data into workflow validation rules (NC-SA-2021-001)

18th November 2020

Risk level: Low

CVSS v3 Base Score: 5.7 (AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H)

CWE: Denial of Service (CWE-400)

HackerOne report: 1018146


A missing input validation in Nextcloud Server 20.0.1 allowed users to store unlimited data in workflow rules causing load and potential DDoS on later interactions and usage with those rules.

Affected Software

  • Nextcloud Server < 20.0.2 (CVE-2020-8293)
  • Nextcloud Server < 19.0.5 (CVE-2020-8293)
  • Nextcloud Server < 18.0.11 (CVE-2020-8293)

Action Taken

The error has been fixed.


It is recommended that the Nextcloud Server is upgraded to 20.0.2.


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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