An issue was discovered in Avira Free Security Suite 10. The permissive access rights on the SoftwareUpdater folder (files / folders and configuration) are incompatible with the privileged file manipulation performed by the product. Files can be created that can be used by an unprivileged user to obtain SYSTEM privileges. Arbitrary file creation can be achieved by abusing the SwuConfig.json file creation: an unprivileged user can replace these files by pseudo-symbolic links to arbitrary files. When an update occurs, a privileged service creates a file and sets its access rights, offering write access to the Everyone group in any directory.
The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.