A security bug in Systemd can be exploited over the network to, at best, potentially crash a vulnerable Linux machine, or, at worst, execute malicious code on the box.
The flaw therefore puts Systemd-powered Linux computers – specifically those using systemd-networkd – at risk of remote hijacking: maliciously crafted DHCPv6 packets can try to exploit the programming cockup and arbitrarily change parts of memory in vulnerable systems, leading to potential code execution. This code could install malware, spyware, and other nasties, if successful.
The vulnerability – which was made public this week – sits within the written-from-scratch DHCPv6 client of the open-source Systemd management suite, which is built into various flavors of Linux.
This client is activated automatically if IPv6 support is enabled, and relevant packets arrive for processing. Thus, a rogue DHCPv6 server on a network, or in an ISP, could emit specially crafted router advertisement messages that wake up these clients, exploit the bug, and possibly hijack or crash vulnerable Systemd-powered Linux machines.
Here’s the Red Hat Linux summary:
systemd-networkd is vulnerable to an out-of-bounds heap write in the DHCPv6 client when handling options sent by network adjacent DHCP servers. A attacker could exploit this via malicious DHCP server to corrupt heap memory on client machines, resulting in a denial of service or potential code execution.