Out-of-bounds read in Linux kernel - CVE-2021-4093

Vulnerability identifier: #VU95678

CSH Severity: Low

CVSS v4: 8.5 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2021-4093

CWE-ID: CWE-125

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to escalate privileges on the system.

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.

Linux kernel
Ubuntu
linux-image-5.11.0-1028-oracle (Ubuntu package)
linux-image-5.11.0-1028-azure (Ubuntu package)
linux-image-oracle (Ubuntu package)
linux-image-aws (Ubuntu package)
linux-image-azure (Ubuntu package)
linux-image-5.11.0-1029-gcp (Ubuntu package)
linux-image-gcp (Ubuntu package)
linux-image-5.13.0-28-generic-64k (Ubuntu package)
linux-image-5.13.0-28-lowlatency (Ubuntu package)
linux-image-5.13.0-28-generic (Ubuntu package)
linux-image-5.13.0-28-generic-lpae (Ubuntu package)
linux-image-generic-hwe-20.04 (Ubuntu package)
linux-image-generic-64k-hwe-20.04 (Ubuntu package)
linux-image-generic-lpae-hwe-20.04 (Ubuntu package)
linux-image-lowlatency-hwe-20.04 (Ubuntu package)
linux-image-virtual-hwe-20.04 (Ubuntu package)
linux-image-lowlatency (Ubuntu package)
linux-image-generic-64k (Ubuntu package)
linux-image-generic-lpae (Ubuntu package)
linux-image-generic (Ubuntu package)
linux-image-virtual (Ubuntu package)
linux-image-oem-20.04 (Ubuntu package)
linux-image-kvm (Ubuntu package)
linux-image-5.13.0-1011-kvm (Ubuntu package)
linux-image-5.13.0-1012-aws (Ubuntu package)
linux-image-gke (Ubuntu package)
linux-image-5.13.0-1013-gcp (Ubuntu package)
linux-image-5.13.0-1016-raspi (Ubuntu package)
linux-image-5.13.0-1016-raspi-nolpae (Ubuntu package)
linux-image-5.13.0-1016-oracle (Ubuntu package)
linux-image-raspi-nolpae (Ubuntu package)
linux-image-raspi (Ubuntu package)
linux-image-oem-20.04c (Ubuntu package)
linux-image-5.13.0-1029-oem (Ubuntu package)

Install update from vendor's repository.

linux-image-5.11.0-1028-oracle (Ubuntu package) - update to 5.11.0-1028.31~20.04.1
linux-image-5.11.0-1028-azure (Ubuntu package) - update to 5.11.0-1028.31~20.04.2
linux-image-oracle (Ubuntu package) - addressed in versions 5.11.0.1028.31~20.04.20, 5.13.0.1016.16
linux-image-aws (Ubuntu package) - addressed in versions 5.11.0.1028.31~20.04.26, 5.13.0.1012.13
linux-image-azure (Ubuntu package) - update to 5.11.0.1028.31~20.04.26
linux-image-5.11.0-1029-gcp (Ubuntu package) - update to 5.11.0-1029.33~20.04.3
linux-image-gcp (Ubuntu package) - addressed in versions 5.11.0.1029.33~20.04.27, 5.13.0.1013.12
linux-image-5.13.0-28-generic-64k (Ubuntu package) - update to 5.13.0-28.31~20.04.1
linux-image-5.13.0-28-lowlatency (Ubuntu package) - update to 5.13.0-28.31~20.04.1
linux-image-5.13.0-28-generic (Ubuntu package) - update to 5.13.0-28.31~20.04.1
linux-image-5.13.0-28-generic-lpae (Ubuntu package) - update to 5.13.0-28.31~20.04.1
linux-image-generic-hwe-20.04 (Ubuntu package) - update to 5.13.0.28.31~20.04.15
linux-image-generic-64k-hwe-20.04 (Ubuntu package) - update to 5.13.0.28.31~20.04.15
linux-image-generic-lpae-hwe-20.04 (Ubuntu package) - update to 5.13.0.28.31~20.04.15
linux-image-lowlatency-hwe-20.04 (Ubuntu package) - update to 5.13.0.28.31~20.04.15
linux-image-virtual-hwe-20.04 (Ubuntu package) - update to 5.13.0.28.31~20.04.15
linux-image-lowlatency (Ubuntu package) - update to 5.13.0.28.38
linux-image-generic-64k (Ubuntu package) - update to 5.13.0.28.38
linux-image-generic-lpae (Ubuntu package) - update to 5.13.0.28.38
linux-image-generic (Ubuntu package) - update to 5.13.0.28.38
linux-image-virtual (Ubuntu package) - update to 5.13.0.28.38
linux-image-oem-20.04 (Ubuntu package) - update to 5.13.0.28.38
linux-image-kvm (Ubuntu package) - update to 5.13.0.1011.11
linux-image-5.13.0-1011-kvm (Ubuntu package) - update to 5.13.0-1011.12
linux-image-5.13.0-1012-aws (Ubuntu package) - update to 5.13.0-1012.13
linux-image-gke (Ubuntu package) - update to 5.13.0.1013.12
linux-image-5.13.0-1013-gcp (Ubuntu package) - update to 5.13.0-1013.16
linux-image-5.13.0-1016-raspi (Ubuntu package) - update to 5.13.0-1016.18
linux-image-5.13.0-1016-raspi-nolpae (Ubuntu package) - update to 5.13.0-1016.18
linux-image-5.13.0-1016-oracle (Ubuntu package) - update to 5.13.0-1016.20
linux-image-raspi-nolpae (Ubuntu package) - update to 5.13.0.1016.21
linux-image-raspi (Ubuntu package) - update to 5.13.0.1016.21
linux-image-oem-20.04c (Ubuntu package) - update to 5.13.0.1029.31
linux-image-5.13.0-1029-oem (Ubuntu package) - update to 5.13.0-1029.36

• https://bugs.chromium.org/p/project-zero/issues/detail?id=2222
• https://bugzilla.redhat.com/show_bug.cgi?id=2028584

• Out-of-bounds read in Linux kernel
• Ubuntu update for linux