CVE-2020-27171

A flaw was found in the Linux kernels eBPF verification code. By default accessing the eBPF verifier is only accessible to privileged users with CAP_SYS_ADMIN. A flaw that triggers Integer underflow when restricting speculative pointer arithmetic allows unprivileged local users to leak the content of kernel memory. The highest threat from this vulnerability is to data confidentiality.

The default Red Hat Enterprise Linux kernel differs from the upstream, that prevents unprivileged users from being able to use eBPF by the kernel.unprivileged_bpf_disabled sysctl.

The setting of 1 would mean that unprivileged users can not use eBPF (which is a default setting), and this mitigating the flaw.

This would require a privileged user with CAP_SYS_ADMIN or root to be able to abuse this flaw reducing its attack space, and may even cause a denial-of-service problem.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

The default Red Hat Enterprise Linux kernel prevents unprivileged users from being able to use eBPF by the kernel.unprivileged_bpf_disabled sysctl. This would require a privileged user with CAP_SYS_ADMIN or root to be able to abuse this flaw reducing its attack space.

For the Red Hat Enterprise Linux 7 the eBPF for unprivileged users is always disabled. For the Red Hat Enterprise Linux 8 to confirm the current state, inspect the sysctl with the command:

cat /proc/sys/kernel/unprivileged_bpf_disabled

The setting of 1 would mean that unprivileged users can not use eBPF, mitigating the flaw.