CVE-2021-3656

EPSS 0.7%CWE-862

Vexday Risk Score

3Low

SSVC decision (CISA)

Track

No exploitation signal → monitor

CVSS —EPSS 0.7%KEV nãoPoC —Nuclei —Metasploit —Patch —

Lifecycle

04 Mar 2022Published on NVD

Recommendation: Monitor — no exploitation signal at the moment.

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 products

n/a · KVM

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References

https://bugzilla.redhat.com/show_bug.cgi?id=1983988 https://github.com/torvalds/linux/commit/c7dfa4009965a9b2d7b329ee970eb8da0d32f0bc https://git.kernel.org/pub/scm/virt/kvm/kvm.git/commit/?id=c7dfa4009965a9b2d7b329ee970eb8da0d32f0bc https://www.openwall.com/lists/oss-security/2021/08/16/1