Security vulnerabilities have been discovered in a range of nix-based operating systems, and Linux, OpenBSD and FreeBSD are all vulnerable.
It's a known vulnerability going back to 2005, but, despite various protection added to help stop this, the vulnerability is still proven, and, clearly, it's felt that it's worthwhile patching the systems now.
Administrators should patch their systems as soon as possible as the new patches are released. The best bet is to contact the developer and look out for a security advisory or a patch.

Such local privilege escalation vulnerabilities can also pose a serious threat to server host providers because one customer can exploit the flaw to gain control over other customer processes running on the same server. Qualys said it's also possible that Stack Clash could be exploited in a way that allows it to remotely execute code directly.

"This is a fairly straightforward way to get root after you've already gotten some sort of user-level access," Jimmy Graham, director of product management at Qualys, told Ars. The attack works by causing a region of computer memory known as the stack to collide into separate memory regions that store unrelated code or data. "The concept isn't new, but this specific exploit is definitely new." "Stack Clash" Privilege Escalation Bug in Unix Operating Systems [arstechnica.com]