Lack of authenticity of metadata keys allows a malicious server to gain access to E2EE folders

Description

Impact

A malicious server administrator can gain full access to an E2EE folder. They can decrypt files, recover the folder structure and add new files.​

Patches

It is recommended that the Nextcloud Desktop client is upgraded to 3.8.0
It is recommended that the Nextcloud Android app is upgraded to 3.25.0
It is recommended that the Nextcloud Android app is upgraded to 4.8.0

Workarounds

• No workaround available

References

• PullRequest
• Thesis by Daniele Coppola

Credit

• Martin Albrecht (Royal Holloway, University of London/Kings College London)
• Matilda Backendal (ETH Zurich)
• Daniele Coppola (ETH Zurich)
• Kenneth G. Paterson (ETH Zurich)

For more information

If you have any questions or comments about this advisory:

• Create a post in nextcloud/security-advisories
• Customers: Open a support ticket at support.nextcloud.com