Log in Start free

Vulnerability · Published Mar 4, 2022 · Assigned by redhat

CVE-2021-3656

High 8.8

In plain English

A high-severity missing authorization in KVM. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 52% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. Fixed versions are available - upgrade the affected package.

Severity (CVSS NVD)8.8High
Exploit odds (30 days)0.7%top 48.3% of all CVEs
Exploited in the wildNo reportsnot in CISA KEV
Attack tooling1Public PoC

Official description

A flaw was found in the KVM's AMD code for supporting SVM nested virtualization. The flaw occurs when processing the VMCB (virtual machine control block) provided by the L1 guest to spawn/handle a nested guest (L2). Due to improper validation of the "virt_ext" field, this issue could allow a malicious L1 to disable both VMLOAD/VMSAVE intercepts and VLS (Virtual VMLOAD/VMSAVE) for the L2 guest. As a result, the L2 guest would be allowed to read/write physical pages of the host, resulting in a crash of the entire system, leak of sensitive data or potential guest-to-host escape.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
AlmaLinux:8kernel-tools-libs-devel4.18.0-305.25.1.el8_4ALSA-2021:4056
Debian:12linux5.14.6-1DEBIAN-CVE-2021-3656
Debian:13linux5.14.6-1DEBIAN-CVE-2021-3656
Debian:14linux5.14.6-1DEBIAN-CVE-2021-3656
Rocky Linux:8kernel0:4.18.0-305.25.1.el8_4RLSA-2021:4056
Rocky Linux:8kernel-rt0:4.18.0-305.25.1.rt7.97.el8_4RLSA-2021:4088
Ubuntu:22.04:LTSlinux-intel-iot-realtimeno fix listedUBUNTU-CVE-2021-3656
Ubuntu:24.04:LTSlinux-raspi-realtimeno fix listedUBUNTU-CVE-2021-3656
Ubuntu:22.04:LTSlinux-realtimeno fix listedUBUNTU-CVE-2021-3656

Affected products (as reported)

VendorProductVersions
n/a KVM Fixed-In v5.14-rc7 and above

Weakness: CWE-862

References