What is the Stack Clash?
The Stack Clash is a vulnerability in the memory management of several operating systems. It affects Linux, OpenBSD, NetBSD, FreeBSD and Solaris, on i386 and amd64. It can be exploited by attackers to corrupt memory and execute arbitrary code.
Qualys researchers discovered this vulnerability and developed seven exploits and seven proofs of concept for this weakness, then worked closely with vendors to develop patches. As a result we are releasing this advisory today as a coordinated effort, and patches for all distributions are available June 19, 2017. We strongly recommend that users place a high priority on patching these vulnerabilities immediately.
What is the Stack Clash vulnerability, precisely?
Each program running on a computer uses a special memory region called the stack. This memory region is special because it grows automatically when the program needs more stack memory. But if it grows too much and gets too close to another memory region, the program may confuse the stack with the other memory region. An attacker can exploit this confusion to overwrite the stack with the other memory region, or the other way around.
More:
https://blog.qualys.com/securitylabs/2017/06/19/the-stack-clashI don't use Linux, but I know several here do.