What’s Vulnerable › Vulnerabilities

CVE-2021-37631: Circle can be accessed by non-Circle members in Nextcloud Deck

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-09-07 · updated 2026-06-17
• Weakness: CWE-639

Description

Deck is an open source kanban style organization tool aimed at personal planning and project organization for teams integrated with Nextcloud. In affected versions the Deck application didn't properly check membership of users in a Circle. This allowed other users in the instance to gain access to boards that have been shared with a Circle, even if the user was not a member of the circle. It is recommended that Nextcloud Deck is upgraded to 1.5.1, 1.4.4 or 1.2.9. If you are unable to update it is advised to disable the Deck plugin.

Affected products

• Nextcloud Deck: before 1.2.9; from 1.3.0 before 1.4.4; from 1.5.0 before 1.5.1 — fixed in 1.2.9, 1.4.4, 1.5.1

How to fix

Upgrade to a fixed version: Nextcloud Deck 1.2.9, 1.4.4, 1.5.1. Check the vendor advisory for mitigations.

References

• https://github.com/nextcloud/deck/pull/3217
• https://github.com/nextcloud/security-advisories/security/advisories/GHSA-4mxp-j277-82hr
• https://hackerone.com/reports/1256021
• https://hackerone.com/reports/1280931
• https://github.com/nextcloud/deck/pull/3217
• https://github.com/nextcloud/security-advisories/security/advisories/GHSA-4mxp-j277-82hr
• https://hackerone.com/reports/1256021
• https://hackerone.com/reports/1280931

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