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redhatcveRedhat.comRH:CVE-2020-27170
HistoryMar 19, 2021 - 10:55 a.m.

CVE-2020-27170

2021-03-1910:55:22
redhat.com
access.redhat.com
28

CVSS2

1.9

Attack Vector

LOCAL

Attack Complexity

MEDIUM

Authentication

NONE

Confidentiality Impact

PARTIAL

Integrity Impact

NONE

Availability Impact

NONE

AV:L/AC:M/Au:N/C:P/I:N/A:N

CVSS3

4.7

Attack Vector

LOCAL

Attack Complexity

HIGH

Privileges Required

LOW

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

NONE

Availability Impact

NONE

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N

EPSS

0.001

Percentile

17.2%

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 local user with the ability to insert eBPF instructions can use the eBPF verifier to abuse a spectre like flaw where they can infer all system memory.

Mitigation

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.

A kernel update will be required to mitigate the flaw for the root or users with CAP_SYS_ADMIN capabilities.

CVSS2

1.9

Attack Vector

LOCAL

Attack Complexity

MEDIUM

Authentication

NONE

Confidentiality Impact

PARTIAL

Integrity Impact

NONE

Availability Impact

NONE

AV:L/AC:M/Au:N/C:P/I:N/A:N

CVSS3

4.7

Attack Vector

LOCAL

Attack Complexity

HIGH

Privileges Required

LOW

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

NONE

Availability Impact

NONE

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N

EPSS

0.001

Percentile

17.2%