Description
An issue was discovered in SDDM through 0.17.0. If configured with ReuseSession=true, the password is not checked for users with an already existing session. Any user with access to the system D-Bus can therefore unlock any graphical session. This is related to daemon/Display.cpp and helper/backend/PamBackend.cpp.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | sddm | 0.18.0-1 | — |
| Debian 13 | sddm | 0.18.0-1 | — |
| Debian 12 | sddm | 0.18.0-1 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 18.04 LTS | sddm | No fix yet | — |
| Ubuntu 16.04 LTS | sddm | No fix yet | — |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | sddm | 0.19.0-4.2 | openSUSE-SU-2024:11376-1 |
Advisories 1
- openSUSE-SU-2024:11376-1 sddm-0.19.0-4.2 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026