CVE-2021-3656
Published: 04 March 2022
Summary
CVE-2021-3656 is a high-severity Missing Authorization (CWE-862) vulnerability in Linux Linux Kernel. Its CVSS base score is 8.8 (High).
Operationally, ranked at the 20.6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2021-26951
Vulnerability details
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…
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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.
- CWE(s)
Related Threats
No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Requiring an access control policy ensures authorization checks are defined and applied for critical functions.
Reviews of access controls detect missing authorization checks on critical functions or resources.
Documenting permitted unauthenticated actions prevents missing authorization by making all exceptions explicit and subject to organizational review.
Requiring attribute association with information prevents authorization from being performed without necessary security or privacy context.
Mandating authorization prior to allowing remote connections addresses missing authorization for remote access.
Mandating authorization before wireless connections are allowed prevents missing authorization for wireless access.
The control requires authorization before allowing mobile device connections, directly mitigating missing authorization for system access.
Requiring approvals for account creation and specifying authorizations ensures authorization is not missing for system access.