CVE-2021-4093 Memory corruption in kernel

What is CVE-2021-4093?

CVE-2021-4093 is a high-severity memory corruption vulnerability in Canonical Ubuntu Linux, published on 18 Feb 2022. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

A flaw was found in the KVM's AMD code for supporting the Secure Encrypted Virtualization-Encrypted State (SEV-ES). A KVM guest using SEV-ES can trigger out-of-bounds reads and writes in the host kernel via a malicious VMGEXIT for a string I/O instruction (for example, outs or ins) using the exit reason SVM_EXIT_IOIO. This issue results in a crash of the entire system or a potential guest-to-host escape scenario.

Weakness: CWE-787, CWE-125

Which versions are affected by CVE-2021-4093?

It affects 4 products.

Products include Canonical Ubuntu Linux, Fedoraproject Fedora, Linux kernel, Redhat Enterprise Linux.

How do I fix CVE-2021-4093?

Apply the vendor's patch.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2021-4093 being exploited?

There is no known exploitation of CVE-2021-4093 in the wild and no public exploit code.

Other vulnerabilities in Canonical Ubuntu Linux

• CVE-2020-11651 SaltStack Salt Authentication Bypass Exploited Critical 9.8
• CVE-2020-7247 OpenSMTPD Remote Code Execution Exploited Critical 9.8
• CVE-2019-16928 Exim Out-of-bounds Write Exploited Critical 9.8
• CVE-2018-6789 Exim Buffer Overflow Exploited Critical 9.8
• CVE-2015-2590 Oracle Java SE and Java SE Embedded Remote Code Execution Exploited Critical 9.8

All Canonical Ubuntu Linux vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2021-4093, GHSA-2vg6-vx3w-m2r4, UBUNTU-CVE-2021-4093.