Description
Flatpak's process ID namespace separation does not prevent a sandboxed app's kill(0, signal) or killpg(0, signal) calls from reaching processes outside the sandbox that share the same process group. A malicious or compromised Flatpak app can use this to cause denial of service by terminating processes outside its sandbox, such as the desktop shell.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Red Hat | Red Hat Enterprise Linux 10 | — | — |
| Red Hat | Red Hat Enterprise Linux 7 | — | — |
| Red Hat | Red Hat Enterprise Linux 8 | — | — |
| Red Hat | Red Hat Enterprise Linux 9 | — | — |
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 | flatpak | 1.18.4-1 | — |
| Debian 13 | flatpak | 1.16.6-1~deb13u3 | — |
| Debian 12 | flatpak | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | flatpak | No fix yet | — |
| Ubuntu 26.04 LTS | flatpak | No fix yet | — |
Show 4 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 24.04 LTS | flatpak | No fix yet | — |
| Ubuntu Pro 22.04 LTS | flatpak | No fix yet | — |
| Ubuntu Pro 20.04 LTS | flatpak | No fix yet | — |
| Ubuntu Pro 18.04 LTS | flatpak | No fix yet | — |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | flatpak | 1.18.4-1.1 | openSUSE-SU-2026:11918-1 |
Advisories 1
- openSUSE-SU-2026:11918-1 flatpak-1.18.4-1.1 on GA media SUSE / openSUSE Security Updates · Sep 30, 2026