What’s Vulnerable › Vulnerabilities

CVE-2020-27777

• Severity: medium (CVSS 6.7 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2020-12-15 · updated 2026-06-17
• Weakness: CWE-862

Description

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.

Affected products

• Linux kernel: before 4.14.204; from 4.15 before 4.19.155; from 4.20 before 5.4.75; from 5.5 before 5.9.5 — fixed in 4.14.204, 4.19.155, 5.4.75, 5.9.5
• Red Hat Enterprise Linux: 5.0, 6.0, 7.0, 8.0
• Red Hat OpenShift Container Platform 4.18: 4.4, 4.5, 4.6

How to fix

Upgrade to a fixed version: Linux kernel 4.14.204, 4.19.155, 5.4.75, 5.9.5. Check the vendor advisory for mitigations.

References

• https://bugzilla.redhat.com/show_bug.cgi?id=1900844
• https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/commit/?h=next&id=bd59380c5ba4147dcbaad3e582b55ccfd120b764
• https://www.openwall.com/lists/oss-security/2020/10/09/1
• https://www.openwall.com/lists/oss-security/2020/11/23/2
• https://bugzilla.redhat.com/show_bug.cgi?id=1900844
• https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/commit/?h=next&id=bd59380c5ba4147dcbaad3e582b55ccfd120b764
• https://www.openwall.com/lists/oss-security/2020/10/09/1
• https://www.openwall.com/lists/oss-security/2020/11/23/2

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