CVE-2021-32679 Information

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.

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Reference

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

Attack Complexity

LOW

Privileges Required

NONE

User Interaction Required

NONE

Scope

REQUIRED

Confidentiality Impact

UNCHANGED

Integrity Impact

HIGH

Availability Impact

HIGH

Base Score

HIGH

Base Severity

8.8