The latest version of Ubuntu Server was revealed to have a local privilege escalation vulnerability. This vulnerability (CVE-2017-16995) has been fixed in previous versions, but it has reappeared in the latest version. The attacker can directly gain root privileges through this vulnerability.
PriorityHighDescriptionThe check_alu_op function in kernel/bpf/verifier.c in the Linux kernel through 4.14.8 allows local users to cause a denial of service (memory corruption) or possibly have unspecified other impact by leveraging incorrect sign extension.Ubuntu-DescriptionJann Horn discovered that the Berkeley Packet Filter (BPF) implementation in the Linux kernel improperly performed sign extension in some situations. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code.
Solution
At present, Ubuntu has not released any patches for the time being. But you can fix this flaws by manual:
$ sudo sysctl kernel.unprivileged_bpf_disabled=1
$ echo kernel.unprivileged_bpf_disabled=1 | \
sudo tee /etc/sysctl.d/90-CVE-2017-16995-CVE-2017-16996.conf
Source: canonical
