{"id":"CVE-2021-29657","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-29657","generatedAt":"2026-10-27T22:25:22.781Z","title":"arch/x86/kvm/svm/nested.c in the Linux kernel before 5.11.12 has a use-after-free in which an AMD KVM guest can bypass access control on host OS MSRs when there are nested guests, aka CID-a58d9166a756.","description":"arch/x86/kvm/svm/nested.c in the Linux kernel before 5.11.12 has a use-after-free in which an AMD KVM guest can bypass access control on host OS MSRs when there are nested guests, aka CID-a58d9166a756. This occurs because of a TOCTOU race condition associated with a VMCB12 double fetch in nested_svm_vmrun.","published":"2021-07-22T17:15:09.000Z","lastModified":"2026-06-17T03:48:06.000Z","status":"Modified","sourceIdentifier":"cve@mitre.org","cvss":{"version":"3.1","score":7.4,"severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"},"cwe":["CWE-367","CWE-416"],"affected":["linux/linux kernel"],"epss":{"score":0.00416,"percentile":0.35643,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.42%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"http://packetstormsecurity.com/files/163324/KVM-nested_svm_vmrun-Double-Fetch.html","tags":["Third Party Advisory","VDB Entry"],"source":"cve@mitre.org"},{"url":"https://bugs.chromium.org/p/project-zero/issues/detail?id=2177","tags":["Exploit","Mailing List","Patch","Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.12","tags":["Exploit","Patch","Vendor Advisory"],"source":"cve@mitre.org"},{"url":"https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a58d9166a756a0f4a6618e4f593232593d6df134","tags":["Patch","Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://security.netapp.com/advisory/ntap-20210902-0008/","tags":["Third Party Advisory"],"source":"cve@mitre.org"},{"url":"http://packetstormsecurity.com/files/163324/KVM-nested_svm_vmrun-Double-Fetch.html","tags":["Third Party Advisory","VDB Entry"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://bugs.chromium.org/p/project-zero/issues/detail?id=2177","tags":["Exploit","Mailing List","Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.12","tags":["Exploit","Patch","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a58d9166a756a0f4a6618e4f593232593d6df134","tags":["Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://security.netapp.com/advisory/ntap-20210902-0008/","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-29657","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}