An issue was discovered in SDDM before 0.19.0. It incorrectly starts the X server in a way that - for a short time period - allows local unprivileged users to create a connection to the X server without providing proper authentication. A local attacker can thus access X server display contents and, for example, intercept keystrokes or access the clipboard. This is caused by a race condition during Xauthority file creation.
| Software | From | Fixed in |
|---|---|---|
| sddm_project / sddm | - | 0.19.0 |
| opensuse / leap | 15.1 | 15.1.x |
| opensuse / leap | 15.2 | 15.2.x |
| debian / debian_linux | 9.0 | 9.0.x |
| debian / debian_linux | 10.0 | 10.0.x |
| fedoraproject / fedora | 33 | 33.x |