Headline
CVE-2021-32802: Preview generation used third-party library not suited for user-generated content
Nextcloud server is an open source, self hosted personal cloud. Nextcloud supports rendering image previews for user provided file content. For some image types, the Nextcloud server was invoking a third-party library that wasn’t suited for untrusted user-supplied content. There are several security concerns with passing user-generated content to this library, such as Server-Side-Request-Forgery, file disclosure or potentially executing code on the system. The risk depends on your system configuration and the installed library version. It is recommended that the Nextcloud Server is upgraded to 20.0.12, 21.0.4 or 22.1.0. These versions do not use this library anymore. As a workaround users may disable previews by setting enable_previews to false in config.php.
Impact
Nextcloud supports rendering image previews for user provided file content. For some image types, the Nextcloud server was invoking a third-party library that wasn’t suited for untrusted user-supplied content.
There are several security concerns with passing user-generated content to this library, such as Server-Side-Request-Forgery, file disclosure or potentially executing code on the system. The risk depends on your system configuration and the installed library version.
Patches
It is recommended that the Nextcloud Server is upgraded to 20.0.12, 21.0.4 or 22.1.0. These versions do not use this library anymore.
Workarounds
Disable previews by setting enable_previews to false in config.php. (documentation)
References
- HackerOne
For more information
If you have any questions or comments about this advisory:
- Create a post in nextcloud/security-advisories
- Customers: Open a support ticket at support.nextcloud.com
Related news
Gentoo Linux Security Advisory 202208-17 - Multiple vulnerabilities have been found in Nextcloud, the worst of which could result in denial of service. Versions less than 23.0.4 are affected.