CVE-2020-8293Network attack vector

Service interruption via unbounded workflow rule data

Published Jan 26, 2021 · Updated Aug 4, 2024

Resource exhaustion in Nextcloud Server before 20.0.2, 19.0.5, or 18.0.11 allows remote authenticated users to interrupt service. The workflow engine accepts and persists unbounded operation and check values in workflow rules, so later rule evaluation consumes excessive server resources. Any authenticated user who can create workflow rules can expand stored rule data; triggering or otherwise using those rules can overload the service.

CVSS severity6.5
Medium
EPSS probability1.56%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Resource exhaustion in Nextcloud Server before 20.0.2, 19.0.5, or 18.0.11 allows remote authenticated users to interrupt service. The workflow engine accepts and persists unbounded operation and check values in workflow rules, so later rule evaluation consumes excessive server resources. Any authenticated user who can create workflow rules can expand stored rule data; triggering or otherwise using those rules can overload the service.

The record

CVE
CVE-2020-8293
Published
Jan 26, 2021
Updated
Aug 4, 2024
Vendor
Nextcloud GmbH
Product
Nextcloud Server
Classifications
CWE-400, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 26, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=Fixed in 20.0.2, 19.0.5, 18.0.11

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Nextcloud GmbH · Nextcloud Serverversion=Fixed in 20.0.2, 19.0.5, 18.0.11

Published CVSS scores

4.0NIST NVDAV:N/AC:L/Au:S/C:N/I:N/A:P
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo