CVE-2021-29657

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{"affected": [{"affectedData": [{"product": "n/a", "vendor": "n/a", "versions": [{"status": "affected", "version": "n/a"}]}], "source": "cve@mitre.org"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "EC50161C-1BB2-406D-8DA1-1A7F5F473581", "versionEndExcluding": "5.10.28", "versionStartIncluding": "5.10", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "4D2300F5-4A31-4893-A7E9-F2B13748BF38", "versionEndExcluding": "5.11.12", "versionStartIncluding": "5.11", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "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."}, {"lang": "es", "value": "El archivo arch/x86/kvm/svm/nested.c en el kernel de Linux versiones anteriores a 5.11.12, presenta un uso de memoria previamente liberada en el que un invitado KVM de AMD puede omitir el control de acceso en los MSR del SO anfitri\u00f3n cuando se presentan invitados anidados, tambi\u00e9n se conoce como CID-a58d9166a756. Esto ocurre debido a una condici\u00f3n de carrera TOCTOU asociada con un doble fetch VMCB12 en la funci\u00f3n nested_svm_vmrun"}], "id": "CVE-2021-29657", "lastModified": "2026-06-17T03:48:06.127", "metrics": {"cvssMetricV2": [{"acInsufInfo": false, "baseSeverity": "MEDIUM", "cvssData": {"accessComplexity": "MEDIUM", "accessVector": "LOCAL", "authentication": "NONE", "availabilityImpact": "COMPLETE", "baseScore": 6.9, "confidentialityImpact": "COMPLETE", "integrityImpact": "COMPLETE", "vectorString": "AV:L/AC:M/Au:N/C:C/I:C/A:C", "version": "2.0"}, "exploitabilityScore": 3.4, "impactScore": 10.0, "obtainAllPrivilege": false, "obtainOtherPrivilege": false, "obtainUserPrivilege": false, "source": "nvd@nist.gov", "type": "Primary", "userInteractionRequired": false}], "cvssMetricV31": [{"cvssData": {"attackComplexity": "HIGH", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 7.4, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 1.4, "impactScore": 5.9, "source": "nvd@nist.gov", "type": "Primary"}]}, "published": "2021-07-22T17:15:09.470", "references": [{"source": "cve@mitre.org", "tags": ["Third Party Advisory", "VDB Entry"], "url": "http://packetstormsecurity.com/files/163324/KVM-nested_svm_vmrun-Double-Fetch.html"}, {"source": "cve@mitre.org", "tags": ["Exploit", "Mailing List", "Patch", "Third Party Advisory"], "url": "https://bugs.chromium.org/p/project-zero/issues/detail?id=2177"}, {"source": "cve@mitre.org", "tags": ["Exploit", "Patch", "Vendor Advisory"], "url": "https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.12"}, {"source": "cve@mitre.org", "tags": ["Patch", "Third Party Advisory"], "url": "https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a58d9166a756a0f4a6618e4f593232593d6df134"}, {"source": "cve@mitre.org", "tags": ["Third Party Advisory"], "url": "https://security.netapp.com/advisory/ntap-20210902-0008/"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Third Party Advisory", "VDB Entry"], "url": "http://packetstormsecurity.com/files/163324/KVM-nested_svm_vmrun-Double-Fetch.html"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Exploit", "Mailing List", "Patch", "Third Party Advisory"], "url": "https://bugs.chromium.org/p/project-zero/issues/detail?id=2177"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Exploit", "Patch", "Vendor Advisory"], "url": "https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.12"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch", "Third Party Advisory"], "url": "https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a58d9166a756a0f4a6618e4f593232593d6df134"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Third Party Advisory"], "url": "https://security.netapp.com/advisory/ntap-20210902-0008/"}], "sourceIdentifier": "cve@mitre.org", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-367"}, {"lang": "en", "value": "CWE-416"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: KVM: double fetch in nested_svm_vmrun can lead to unrestricted MSR access", "id": "1995153", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=1995153"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.8", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H", "status": "draft"}, "cwe": "CWE-367", "details": ["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.", "A flaw was found in the Linux kernel. A KVM guest on AMD can launch a nested guest without the Intercept VMRUN control bit by exploiting a TOCTOU vulnerability in nested_svm_vmrun. A malicious guest could use this flaw to gain unrestricted access to host MSRs, possibly leading to guest-to-host escape scenario."], "mitigation": {"lang": "en:us", "value": "This vulnerability can be mitigated by disabling the nested virtualization feature:\n```\n# modprobe -r kvm_amd\n# modprobe kvm_amd nested=0\n```"}, "name": "CVE-2021-29657", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-alt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2021-03-31T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2021-29657\nhttps://nvd.nist.gov/vuln/detail/CVE-2021-29657\nhttps://bugs.chromium.org/p/project-zero/issues/detail?id=2177"], "statement": "The nested virtualization feature is not enabled by default up to Red Hat Enterprise Linux 8.4. Most importantly, Red Hat currently provides nested virtualization only as a Technology Preview, and is therefore unsupported for production use. For additional details please see https://access.redhat.com/solutions/21101 and https://access.redhat.com/support/offerings/techpreview.", "threat_severity": "Moderate"}

{}