What’s Vulnerable › Vulnerabilities

CVE-2023-28999: Nextcloud: Lack of authenticity of metadata keys allows a malicious server to gain access to E2EE folders

• Severity: medium (CVSS 6.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2023-04-04 · updated 2026-06-17
• Weakness: CWE-325

Description

Nextcloud is an open-source productivity platform. In Nextcloud Desktop client 3.0.0 until 3.8.0, Nextcloud Android app 3.13.0 until 3.25.0, and Nextcloud iOS app 3.0.5 until 4.8.0, a malicious server administrator can gain full access to an end-to-end encrypted folder. They can decrypt files, recover the folder structure and add new files.​ This issue is fixed in Nextcloud Desktop 3.8.0, Nextcloud Android 3.25.0, and Nextcloud iOS 4.8.0. No known workarounds are available.

Affected products

• Desktop Client: from 3.0.0 before 3.8.0 — fixed in 3.8.0
• com.nextcloud.client: from 3.0.5 before 4.8.0; from 3.13.0 before 3.25.0 — fixed in 3.25.0, 4.8.0

How to fix

Upgrade to a fixed version: Desktop Client 3.8.0; com.nextcloud.client 3.25.0, 4.8.0. Check the vendor advisory for mitigations.

References

• https://ethz.ch/content/dam/ethz/special-interest/infk/inst-infsec/appliedcrypto/education/theses/report_DanieleCoppola.pdf
• https://github.com/nextcloud/desktop/pull/5560
• https://github.com/nextcloud/security-advisories/security/advisories/GHSA-8875-wxww-3rr8
• https://ethz.ch/content/dam/ethz/special-interest/infk/inst-infsec/appliedcrypto/education/theses/report_DanieleCoppola.pdf
• https://github.com/nextcloud/desktop/pull/5560
• https://github.com/nextcloud/security-advisories/security/advisories/GHSA-8875-wxww-3rr8

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