What’s Vulnerable › Vulnerabilities
CVE-2021-32679: Filenames not escaped by default in controllers using DownloadResponse
- Severity: high (CVSS 8.8 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 1.4% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2021-07-12 · updated 2026-06-17
- Weakness: CWE-116
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`.
Affected products
- Fedoraproject Fedora: 33, 34
- Nextcloud Server: before 19.0.13; from 20.0.0 before 20.0.11; from 21.0.0 before 21.0.3 — fixed in 19.0.13, 20.0.11, 21.0.3
How to fix
Upgrade to a fixed version: Nextcloud Server 19.0.13, 20.0.11, 21.0.3. Check the vendor advisory for mitigations.
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/BVZS26RDME2DYTKET5AECRIZDFUGR2AZ/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/J63NBVPR2AQCAWRNDOZSGRY5II4WS2CZ/
- https://security.gentoo.org/glsa/202208-17
- 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/BVZS26RDME2DYTKET5AECRIZDFUGR2AZ/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/J63NBVPR2AQCAWRNDOZSGRY5II4WS2CZ/
- https://security.gentoo.org/glsa/202208-17
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