CVE-2021-32679
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (1.37%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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 3.1
- 8.8 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- EPSS
- 1.37% probability · 70th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-116
- Affected
- nextcloud/nextcloud server · fedoraproject/fedora
- Source
- security-advisories@github.com
References
- https://github.com/nextcloud/security-advisories/security/advisories/GHSA-3hjp-26x8-mhf6Third Party Advisory
- https://github.com/nextcloud/server/pull/27354Patch, Third Party Advisory
- https://hackerone.com/reports/1215263Permissions Required
- 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/202208-17Third Party Advisory
- https://github.com/nextcloud/security-advisories/security/advisories/GHSA-3hjp-26x8-mhf6Third Party Advisory
- https://github.com/nextcloud/server/pull/27354Patch, Third Party Advisory
- https://hackerone.com/reports/1215263Permissions Required
- 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/202208-17Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.