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Fencer Intel
medium 6.7

CVE-2020-27777 json

A flaw was found in the way RTAS handled memory accesses in userspace to kernel communication.

published 5y ago modified 4mo ago also EUVD-2020-20281

cvss
6.7
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 41%
public exploits
0
none known

Summary

A flaw was found in the way RTAS handled memory accesses in userspace to kernel communication. On a locked down (usually due to Secure Boot) guest system running on top of PowerVM or KVM hypervisors (pseries platform) a root like local user could use this flaw to further increase their privileges to that of a running kernel.

Patch / fix

  • linux linux_kernel 4.14.204, 4.19.155, 5.4.75, 5.9.5
  • linux Debian 14, Debian 13, Debian 12 5.9.6-1

debian advisories DEBIAN-CVE-2020-27777

  • linux Ubuntu 16.04 LTS 4.4.0-201.233
  • linux Ubuntu 18.04 LTS 4.15.0-129.132
  • linux Ubuntu 20.04 LTS 5.4.0-59.65
  • linux-hwe Ubuntu 16.04 LTS 4.15.0-129.132~16.04.1
  • linux-gke-5.4 Ubuntu 18.04 LTS 5.4.0-1033.35~18.04.1
  • linux-hwe-5.4 Ubuntu 18.04 LTS 5.4.0-59.65~18.04.1
  • linux-hwe-5.8 Ubuntu 20.04 LTS 5.8.0-44.50~20.04.1
  • linux-dell300x Ubuntu 18.04 LTS 4.15.0-1010.14

ubuntu advisories UBUNTU-CVE-2020-27777

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel RHEL 8 4.18.0-348.el8
  • perf RHEL 8 4.18.0-348.el8
  • bpftool RHEL 8 4.18.0-348.el8
  • kernel-core RHEL 8 4.18.0-348.el8
  • kernel-tools RHEL 8 4.18.0-348.el8
  • python3-perf RHEL 8 4.18.0-348.el8
  • kernel-modules RHEL 8 4.18.0-348.el8
  • kernel-zfcpdump RHEL 8 4.18.0-348.el8

red hat advisories RHSA-2021:4356RHSA-2021:3327

  • kernel-syms SLES for SAP 12 SP3, SLES 12 SP3-LTSS, SLES 12 SP3-BCL +4 more 4.4.180-94.138.1
  • kernel-source SLES for SAP 12 SP3, SLES 12 SP3-LTSS, SLES 12 SP3-BCL +4 more 4.4.180-94.138.1
  • kernel-default SLES for SAP 12 SP3, SLES 12 SP3-LTSS, SLES 12 SP3-BCL +5 more 4.4.180-94.138.1
  • kgraft-patch-SLE12-SP3_Update_37 SLES for SAP 12 SP3, SLES 12 SP3-LTSS, OpenStack Cloud Crowbar 8 +3 more 1-4.3.1
  • kernel-syms SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.66.1
  • kernel-source SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.66.1
  • kernel-default SLES for SAP 15, SLES 15-LTSS, SLE Live Patching 15 +3 more 4.12.14-150.66.1
  • kernel-vanilla SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.66.1

suse advisories SUSE-SU-2021:14630-1SUSE-SU-2021:0452-1SUSE-SU-2021:0438-1SUSE-SU-2021:0437-1SUSE-SU-2021:0434-1SUSE-SU-2021:0133-1

  • kernel-rt openSUSE Leap 15.2 5.3.18-lp152.3.5.1
  • kernel-syms-rt openSUSE Leap 15.2 5.3.18-lp152.3.5.1
  • kernel-rt_debug openSUSE Leap 15.2 5.3.18-lp152.3.5.1
  • kernel-source-rt openSUSE Leap 15.2 5.3.18-lp152.3.5.1
  • kernel-syms openSUSE Leap 15.1 4.12.14-lp151.28.91.1
  • kernel-obs-qa openSUSE Leap 15.1 4.12.14-lp151.28.91.1
  • kernel-source openSUSE Leap 15.1 4.12.14-lp151.28.91.1
  • kernel-default openSUSE Leap 15.1 4.12.14-lp151.28.91.1

opensuse advisories openSUSE-SU-2021:0242-1openSUSE-SU-2021:0075-1openSUSE-SU-2021:0060-1openSUSE-SU-2020:2260-1openSUSE-SU-2020:2193-1openSUSE-SU-2020:2161-1

Is CVE-2020-27777 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-27777 updated cvss 6.4

kernel: powerpc: RTAS calls can be used to compromise kernel integrity

  • Red Hat Enterprise Linux 5 kernel Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 7 perf, kernel, kernel-alt, python-perf, kernel-kdump, kernel-tools, +3 more
    affected: workaround, no fix planned “Will not fix”
  • Red Hat CodeReady Linux Builder (v. 8) kernel-debuginfo-common-x86_64 4.18.0-348.el8, kernel-debuginfo-common-aarch64 4.18.0-348.el8, kernel-debuginfo-common-ppc64le 4.18.0-348.el8 Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-348.el8, kernel 4.18.0-348.el8, bpftool 4.18.0-348.el8, kernel-core 4.18.0-348.el8, kernel-tools 4.18.0-348.el8, python3-perf 4.18.0-348.el8, +15 more
    fixed: vendor fix RHSA-2021:4356
  • Red Hat Enterprise Linux Client (v. 7) perf 3.10.0-1160.41.1.el7, kernel 3.10.0-1160.41.1.el7, bpftool 3.10.0-1160.41.1.el7, python-perf 3.10.0-1160.41.1.el7, kernel-tools 3.10.0-1160.41.1.el7, kernel-tools-libs 3.10.0-1160.41.1.el7, +2 more Red Hat Enterprise Linux Client Optional (v. 7) kernel-debuginfo-common-x86_64 3.10.0-1160.41.1.el7 Red Hat Enterprise Linux ComputeNode Optional (v. 7) kernel-debuginfo-common-x86_64 3.10.0-1160.41.1.el7 Red Hat Enterprise Linux Server (v. 7) perf 3.10.0-1160.41.1.el7, kernel 3.10.0-1160.41.1.el7, bpftool 3.10.0-1160.41.1.el7, python-perf 3.10.0-1160.41.1.el7, kernel-kdump 3.10.0-1160.41.1.el7, kernel-tools 3.10.0-1160.41.1.el7, +7 more Red Hat Enterprise Linux Server Optional (v. 7) kernel-debuginfo-common-ppc64 3.10.0-1160.41.1.el7, kernel-debuginfo-common-x86_64 3.10.0-1160.41.1.el7, kernel-debuginfo-common-ppc64le 3.10.0-1160.41.1.el7 Red Hat Enterprise Linux Workstation (v. 7) perf 3.10.0-1160.41.1.el7, kernel 3.10.0-1160.41.1.el7, bpftool 3.10.0-1160.41.1.el7, python-perf 3.10.0-1160.41.1.el7, kernel-tools 3.10.0-1160.41.1.el7, kernel-tools-libs 3.10.0-1160.41.1.el7, +2 more
    +1 more products
    Red Hat Enterprise Linux Workstation Optional (v. 7) kernel-debuginfo-common-x86_64 3.10.0-1160.41.1.el7
    fixed: vendor fix RHSA-2021:3327
  • Red Hat Enterprise Linux 7 kernel-rt, kernel-rt-kvm, kernel-rt-trace, kernel-rt-debug-kvm, kernel-rt-trace-kvm Red Hat Enterprise Linux 8 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +6 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.48% chance of exploitation in the next 30 days, higher than 41% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • git.kernel.org https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/commit/?h=next&id=bd59380c5ba4147dcbaad3e582b55ccfd120b764 referenced PoC, tagged "exploit" by a source, unverified
  • openwall.com https://www.openwall.com/lists/oss-security/2020/10/09/1 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 6.7 CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.2 AV:L/AC:L/Au:N/C:C/I:C/A:C

Affected products

  • n/a kernel

Classification

Weakness
Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.