CVE-2023-35927: Nextcloud system addressbooks can be modified by malicious trusted server
NextCloud Server and NextCloud Enterprise Server provide file storage for Nextcloud, a self-hosted productivity platform. In NextCloud Server versions 25.0.0 until 25.0.7 and 26.0.0 until 26.0.2 and Nextcloud Enterprise Server versions 21.0.0 until 21.0.9.12, 22.0.0 until 22.2.10.12, 23.0.0 until 23.0.12.7, 24.0.0 until 24.0.12.2, 25.0.0 until 25.0.7, and 26.0.0 until 26.0.2, when two server are registered as trusted servers for each other and successfully exchanged the share secrets, the malicious server could modify or delete VCards in the system addressbook on the origin server. This would impact the available and shown information in certain places, such as the user search and avatar menu. If a manipulated user modifies their own data in the personal settings the entry is fixed again.
Nextcloud Server n 25.0.7 and 26.0.2 and Nextcloud Enterprise Server 21.0.9.12, 22.2.10.12, 23.0.12.7, 24.0.12.2, 25.0.7, and 26.0.2 contain a patch for this issue. A workaround is available. Remove all trusted servers in the "Administration" > "Sharing" settings …/index.php/settings/admin/sharing. Afterwards, trigger a recreation of the local system addressbook with the following occ dav:sync-system-addressbook.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Nextcloud Server/Nextcloud Enterprise Serverto a version that resolves this vulnerability.Fixed in 25.0.7 - Upgrade
Upgrade
Nextcloud Server/Nextcloud Enterprise Serverto a version that resolves this vulnerability.Fixed in 26.0.2 - Upgrade
Upgrade
Nextcloud Enterprise Serverto a version that resolves this vulnerability.Fixed in 21.0.9.12 - Upgrade
Upgrade
Nextcloud Enterprise Serverto a version that resolves this vulnerability.Fixed in 22.2.10.12 - Upgrade
Upgrade
Nextcloud Enterprise Serverto a version that resolves this vulnerability.Fixed in 23.0.12.7 - Upgrade
Upgrade
Nextcloud Enterprise Serverto a version that resolves this vulnerability.Fixed in 24.0.12.2 - Upgrade
Upgrade
Nextcloud Enterprise Serverto a version that resolves this vulnerability.Fixed in 25.0.7 - Upgrade
Upgrade
Nextcloud Enterprise Serverto a version that resolves this vulnerability.Fixed in 26.0.2 - Configuration
In Nextcloud, remove all trusted servers in the "Administration" > "Sharing" settings at /index.php/settings/admin/sharing.
Nextcloud Administration > Sharing (trusted servers) at /index.php/settings/admin/sharing = Remove all trusted servers - Operational
After applying the workaround, trigger a recreation of the local system addressbook by running: occ dav:sync-system-addressbook.
Event History
Frequently Asked Questions
What is the vulnerability ID for this NextCloud Server vulnerability?
The vulnerability ID for this NextCloud Server vulnerability is CVE-2023-35927.
What is the severity of CVE-2023-35927?
The severity of CVE-2023-35927 is high with a CVSS score of 8.1.
Which versions of NextCloud Server and NextCloud Enterprise Server are affected by CVE-2023-35927?
NextCloud Server versions 25.0.0 until 25.0.7 and 26.0.0 until 26.0.2 and Nextcloud Enterprise Server versions 21.0.0 until 21.0.9.12, 22.0.0 until 22.2.10.12, 23.0.0 until 23.0.12.7, 24.0.0 until 24.0.12.2, 25.0.0 until 25.0.7, and 26.0.0 until 26.0.2 are affected by CVE-2023-35927.
How can I fix the CVE-2023-35927 vulnerability?
To fix the CVE-2023-35927 vulnerability, it is recommended to update NextCloud Server to version 26.0.3 or later, and Nextcloud Enterprise Server to version 23.0.12.8 or later.
Where can I find more information about CVE-2023-35927?
More information about CVE-2023-35927 can be found in the following references: [GitHub Security Advisory](https://github.com/nextcloud/security-advisories/security/advisories/GHSA-h7f7-535f-7q87), [Nextcloud Server Pull Request](https://github.com/nextcloud/server/pull/38247), and [HackerOne Report](https://hackerone.com/reports/1976754).