CVE-2021-3656

highpriority · attend · 45OT risk · highEPSS 0.007 · 51 %ileexploit · PoCDEEURUUS

grimoire priorityP1 · Urgent

Exploitable?

Public exploit

1 exploit · PoC

Likely / severe?

0.66% (51st) EPSS

CVSS 7.2 · high

Is it mine?

103 products

Check your exposure

Who says so?

4 sources

cnnvd · enisa_euvd · fstec_bdu · cert_bund

EPSS · scored 2026-10-27

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.

cvss

Technical severity, 0–10. One row per scoring source.

8.8

010

base score 0–10 · higher = more severe · hover a vector to decode

v2.07.2highAV:L/AC:L/Au:N/C:C/I:C/A:Cprimary · NVD / NIST USexploitability 3.9 · impact 10

v3.18.8highCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hprimary · NVD / NIST USexploitability 2 · impact 6

v3.18.8highAV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hsecondary · FSTEC (BDU) RU

v3.18.3highCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:Psecondary · CVSS-BT (t0sche)

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-862USprimaryCWE-264USCWE-862US

exploits (1)

Public proof-of-concept and weaponised exploit code.

rami08448/CVE-2021-3656-Demorami08448/CVE-2021-3656-DemoPoC · poc_in_github

affected products (103)

Products and version ranges known to be affected.

Juniper Contrail Service Orchestrationall versionscert_bundDEcpe:/a:juniper:contrail_service_orchestration:-
Juniper Junos Space <21.3R1all versionscert_bundDE
Juniper Junos Space Security Director <24.1R4all versionscert_bundDE
Juniper Junos Space≤ Security Director <24.1R4cert_bundDE
Juniper Junos Space< 21.3R1cert_bundDE
n/a KVM≤ Fixed-In v5.14-rc7 and aboveenisa_euvdEU
Canonical Ltd. Ubuntu≤ 20.04 LTSfstec_bduRU
Canonical Ltd. Ubuntu≤ 18.04 LTSfstec_bduRU
Novell Inc. SUSE Linux Enterprise≤ High Performance Computing 12 SP5fstec_bduRU
Novell Inc. SUSE Linux Enterprise≤ High Performance Computing 15 SP2fstec_bduRU
Novell Inc. SUSE Linux Enterprise≤ High Performance Computing 15 SP2 ESPOSfstec_bduRU
Novell Inc. SUSE Linux Enterprise≤ High Performance Computing 15 SP2 LTSSfstec_bduRU
Novell Inc. SUSE Linux Enterprise≤ High Performance Computing 15 SP3fstec_bduRU
Novell Inc. SUSE Linux Enterprise≤ Desktop 15 SP4fstec_bduRU
Novell Inc. SUSE Linux Enterprise≤ High Performance Computing 15fstec_bduRU
Novell Inc. SUSE Linux Enterprise≤ High Performance Computing 15-LTSSfstec_bduRU
Novell Inc. SUSE Linux Enterprise≤ High Performance Computing 15 SP1-ESPOSfstec_bduRU
Novell Inc. SUSE Linux Enterprise≤ High Performance Computing 15 SP1-LTSSfstec_bduRU
Novell Inc. SUSE Linux Enterprise≤ Desktop 15 SP3fstec_bduRU
Novell Inc. SUSE Linux Enterprise≤ Desktop 15 SP2fstec_bduRU

showing 20 of 103

advisories (2)

Vendor and ecosystem advisories describing this.

WID-SEC-W-2022-2065Linux Kernel: Mehrere Schwachstellen ermöglichen Denial of ServiceDeutsch2021-08-16csaf · cert_bundDE
Ein lokaler Angreifer kann mehrere Schwachstellen im Linux Kernel ausnutzen, um einen Denial of Service Angriff durchzuführen.
WID-SEC-W-2023-0063Juniper Junos Space: Mehrere SchwachstellenDeutsch2022-01-12csaf · cert_bundDE
Ein Angreifer aus dem angrenzenden Netzwerk oder ein entfernter anonymer, authentisierter oder lokaler Angreifer kann mehrere Schwachstellen in Juniper Junos Space ausnutzen, um Sicherheitsmaßnahmen zu umgehen, vertrauliche Informationen offenzulegen, einen Denial-of-Service-Zustand auszulösen, beliebigen Code auszuführen und seine Privilegien zu erweitern.

also known as (3)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd fstec_bdu cert_bund NVD CVE.org MITRE

published 2022-03-04modified 2026-06-17

related (11,479)

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+11474 more

references (51)

External citations — patches, advisories, analysis.

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