Systemd, the Linux system and service manager, has become more prevalent than init as a Linux startup and control program. However, it has always faced criticism from some quarters. Now, after the discovery of a security bug in systemd by Qualys, systemd will have even more critics.
How bad is the security bug? Well, if a person were to successfully exploit it, they would gain the power to cause a denial of service by triggering a kernel panic. So, it is quite bad.
Bharat Jogi, Qualys’s Senior Manager of Vulnerabilities and Signatures recommended immediate patches.
A house of cards
Jogi wrote that the breadth of the attack surface for the vulnerability warranted his immediate call for patches. Systemd is used in almost all modern Linux distributions, with this particular vulnerability arriving in April 2015.
It works by enabling attackers to misuse the alloca() function in a way that causes memory corruption. The corruption allows the hacker to crash Systemd and the entire operating system with it. Practically, this can be done by a local attacker mounting a filesystem on a very long path.
What happens is, it eats up memory space in the systemd stack, causing it to crash.
Hope in the Red Hat
All of this is bad news, except that Red Hat Product Security and systemd developers have immediately patched the hole. There is no way to deal with this problem except to patch it. While the flaw is not in all distributions, you will find it in distros like the Debian 10 (Buster) and its close relatives like Mint and Ubuntu.
For that reason, it is recommended you patch your version of systemd as soon as possible.