Oracle Linux: CVE-2019-15239: ELSA-2019-3979: kernel security and bug fix update (IMPORTANT) (Multiple Advisories)

In the Linux kernel, a certain net/ipv4/tcp_output.c change, which was properly incorporated into 4.16.12, was incorrectly backported to the earlier longterm kernels, introducing a new vulnerability that was potentially more severe than the issue that was intended to be fixed by backporting. Specifically, by adding to a write queue between disconnection and re-connection, a local attacker can trigger multiple use-after-free conditions. This can result in a kernel crash, or potentially in privilege escalation. NOTE: this affects (for example) Linux distributions that use 4.9.x longterm kernels before 4.9.190 or 4.14.x longterm kernels before 4.14.139.
A flaw was found in the way the Linux kernel's networking subsystem handled the write queue between TCP disconnection and re-connections. A local attacker could use this flaw to trigger multiple use-after-free conditions potentially escalating their privileges on the system.