XDG Desktop Portal is a desktop integration portal. Prior to version 1.22.1, malicious sandboxed applications can use the FileChooser.SaveFiles method to gain arbitrary file access to non-existing files on the host (limited to files the user has access to). The FileChooser.SaveFiles method takes optional filenames which get appended to the selected directory by backends. The backends are supposed to check that the file does not exist yet. The filenames are not validated by the frontend and also not by common backends. This issue has been patched in version 1.22.1.
XDG Desktop Portal: Drag-and-drop and copy-paste theft via predictable FileTransfer key
XDG Desktop Portal is a desktop integration portal. Prior to version 1.22.1, malicious sandboxed applications can use the FileTransfer.RetrieveFiles method to redirect drag-and-drop and copy-paste data targeted at other applications to itself. Some portals generate tokens which provide access to resources. The sharing of the token transfers access to the resource and is supposed to happen out of band. The tokens were generated with g_random_int or g_uuid_string_random, both of which use GLib's GRand based on the Mersenne Twister PRNG which created a stream of reproducible random numbers. By generating enough tokens, the state of the GRand can
USN-8287-1 fixed a vulnerability in XDG Desktop Portal. Unfortunately the
fix for CVE-2026-40354 was incomplete and introduced a regression when
trashing files. This update fixes the problem and provides the
corresponding update for Ubuntu 26.04 LTS.
We apologize for the inconvenience.
Original advisory details:
It was discovered that XDG Desktop Portal incorrectly handled
trashing files. A local attacker could possibly use this issue to
delete arbitrary files on the host file system via a symlink attack.
Flatpak xdg-desktop-portal before 1.20.4 and 1.21.x before 1.21.1 allows any Flatpak app to trash any file in the host context via a symlink attack on g_file_trash.