What’s Vulnerable › Vulnerabilities

CVE-2023-28997: Nextcloud Desktop: Initialization vector reuse in E2EE allows malicious server admin to break, manipulate, access files

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.1% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2023-04-04 · updated 2026-06-17
• Weakness: CWE-323

Description

The Nextcloud Desktop Client is a tool to synchronize files from Nextcloud Server. Starting with version 3.0.0 and prior to version 3.6.5, a malicious server administrator can recover and modify the contents of end-to-end encrypted files. Users should upgrade the Nextcloud Desktop client to 3.6.5 to receive a patch. No known workarounds are available.

Affected products

• Desktop Client: from 3.0.0 before 3.6.5 — fixed in 3.6.5

How to fix

Upgrade to a fixed version: Desktop Client 3.6.5. 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/5324
• https://github.com/nextcloud/security-advisories/security/advisories/GHSA-4p33-rw27-j5fc
• https://ethz.ch/content/dam/ethz/special-interest/infk/inst-infsec/appliedcrypto/education/theses/report_DanieleCoppola.pdf
• https://github.com/nextcloud/desktop/pull/5324
• https://github.com/nextcloud/security-advisories/security/advisories/GHSA-4p33-rw27-j5fc
• https://lists.debian.org/debian-lts-announce/2025/09/msg00018.html

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