CVE-2021-3656

high

Published 2021-11-02 · Modified 2021-11-02

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CVSS v3

—

CVSS v4 NEW

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not yet in upstream

VIR risk

8.0

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.

Predictions

Exploit likelihood

20%

Patch ETA

—

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

No mitigations published for this CVE yet.

The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.

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OS impact

SUSE Affected 1 release

Version	Status	Fixed in
—	Affected	—

Arch Fixed 1 release

Version	Status	Fixed in
—	Fixed	`5.13.13.hardened1-1`

Debian Fixed 5 releases

Version	Status	Fixed in
trixie	Fixed	`5.14.6-1`
sid	Fixed	`5.14.6-1`
forky	Fixed	`5.14.6-1`
bullseye	Fixed	`5.10.46-5`
bookworm	Fixed	`5.14.6-1`

Red Hat Fixed 1 release

Version	Status	Fixed in
8	Fixed	—

Rocky Linux Fixed 1 release

Version	Status	Fixed in
8	Fixed	—

References

Community-verified mitigations for this CVE will appear above when contributors publish them.

Verify integrity in audit chain (admin only). AS-IS.