An issue was discovered in sd-bus in systemd 239. busprocessobject() in libsystemd/sd-bus/bus-objects.c allocates a variable-length stack buffer for temporarily storing the object path of incoming D-Bus messages. An unprivileged local user can exploit this by sending a specially crafted message to PID1, causing the stack pointer to jump over the stack guard pages into an unmapped memory region and trigger a denial of service (systemd PID1 crash and kernel panic).

A use-after-free vulnerability was found in a network namespaces code affecting the Linux kernel since v4.0-rc1 through v4.15-rc5. The function getnetnsbyid() does not check for the net::count value after it has found a peer network in netnsids idr which could lead to double free and memory corruption. This vulnerability could allow an unprivileged local user to induce kernel memory corruption on the system, leading to a crash. Due to the nature of the flaw, privilege escalation cannot be fully ruled out, although we believe it is unlikely.

References:

https://marc.info/?l=linux-netdev&m=151370451121029&w=2

https://marc.info/?t=151370468900001&r=1&w=2 (a whole thread)

http://seclists.org/oss-sec/2018/q1/7

An upstream patch:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=21b5944350052d2583e82dd59b19a9ba94a007f0