A flaw in systemd, the init system used on many Linux systems, can be exploited using a malicious DNS query to either crash a system or to run code remotely. The vulnerability resides in the daemon systemd-resolved and can be triggered using a TCP payload, according to Ubuntu developer Chris Coulson. This component can be tricked into allocating less memory than needed for a look-up. When the reply is bigger it overflows the buffer allowing an attacker to overwrite memory. This would result in the process either crashing or it could allow for code execution remotely. “A malicious DNS server can exploit this by responding with a specially crafted TCP payload to trick systemd-resolved in to allocating a buffer that’s too small, and subsequently write arbitrary data beyond the end of it,” is how Coulson put it.
Affected Linux vendors have pushed out patches — but the bug has apparently been present in systemd code since June of 2015. And long-time Slashdot reader walterbyrd also reports a recently-discovered bug where systemd unit files that contain illegal usernames get defaulted to root.
Read more of this story at Slashdot.