openSUSE maintainers received notification of a supply chain attack against the “xz” compression tool and “liblzma5” library.
Background
Security Researcher Andres Freund reported to Debian that the xz / liblzma library had been backdoored.
This backdoor was introduced in the upstream github xz project with release 5.6.0 in February 2024.
Our rolling release distribution openSUSE Tumbleweed and openSUSE MicroOS included this version between March 7th and March 28th.
SUSE Linux Enterprise and Leap are built in isolation from openSUSE. Code, functionality and characteristics of Tumbleweed are not automatically introduced in SUSE Linux Enterprise and/or Leap. It has been established that the malicious file introduced into Tumbleweed is not present in SUSE Linux Enterprise and/or Leap.
Impact
Current research indicates that the backdoor is active in the SSH Daemon, allowing malicious actors to access systems where SSH is exposed to the internet.
As of March 29th reverse engineering of the backdoor is still ongoing.
Mitigations
openSUSE Maintainers have rolled back the version of xz on Tumbleweed on March 28th and have released a new Tumbleweed snapshot (20240328 or later) that was built from a safe backup.
The reversed version is versioned 5.6.1.revertto5.4 and can be queried with rpm -q liblzma5.
User recommendation
For our openSUSE Tumbleweed users where SSH is exposed to the internet we recommend installing fresh, as it’s unknown if the backdoor has been exploited. Due to the sophisticated nature of the backdoor an on-system detection of a breach is likely not possible. Also rotation of any credentials that could have been fetched from the system is highly recommended. Otherwise, simply update to openSUSE Tumbleweed 20240328 or later and reboot the system.
More Information about openSUSE:
On desktop systems, the SSH server is disabled by default. It should say "disabled" in
systemctl status sshd, then you're good.On server systems, the SSH server is enabled, but you would usually know that it accepts incoming connections from the internet.
So, a home-server would need to be exposed in your modem/router. And if you're hosting on a VPS, well, then it's obviously going to be reachable.