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.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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.
    (CVE-2021-29657)

Note that Nessus relies on the presence of the package as reported by the vendor.

The remote Ubuntu 20.04 LTS host has a package installed that is affected by multiple vulnerabilities as referenced in the USN-4948-1 advisory.

    Ryota Shiga discovered that the eBPF implementation in the Linux kernel did not properly verify that a BPF     program only reserved as much memory for a ring buffer as was allocated. A local attacker could use this     to cause a denial of service (system crash) or execute arbitrary code. (CVE-2021-3489)

    Manfred Paul discovered that the eBPF implementation in the Linux kernel did not properly track bounds on     bitwise operations. A local attacker could use this to cause a denial of service (system crash) or execute     arbitrary code. (CVE-2021-3490)

    Billy Jheng Bing-Jhong discovered that the io_uring implementation of the Linux kernel did not properly     enforce the MAX_RW_COUNT limit in some situations. A local attacker could use this to cause a denial of     service (system crash) or execute arbitrary code. (CVE-2021-3491)

    Kiyin () discovered that the NFC LLCP protocol implementation in the Linux kernel contained a     reference counting error. A local attacker could use this to cause a denial of service (system crash).
    (CVE-2020-25670)

    Kiyin () discovered that the NFC LLCP protocol implementation in the Linux kernel did not properly     deallocate memory in certain error situations. A local attacker could use this to cause a denial of     service (memory exhaustion). (CVE-2020-25671, CVE-2020-25672)

    It was discovered that the Xen paravirtualization backend in the Linux kernel did not properly deallocate     memory in some situations. A local attacker could use this to cause a denial of service (memory     exhaustion). (CVE-2021-28688)

    It was discovered that the io_uring subsystem in the Linux kernel contained a race condition leading to a     deadlock condition. A local attacker could use this to cause a denial of service. (CVE-2021-28951)

    John Stultz discovered that the audio driver for Qualcomm SDM845 systems in the Linux kernel did not     properly validate port ID numbers. A local attacker could use this to cause a denial of service (system     crash) or possibly execute arbitrary code. (CVE-2021-28952)

    Zygo Blaxell discovered that the btrfs file system implementation in the Linux kernel contained a race     condition during certain cloning operations. A local attacker could possibly use this to cause a denial of     service (system crash). (CVE-2021-28964)

    Vince Weaver discovered that the perf subsystem in the Linux kernel did not properly handle certain PEBS     records properly for some Intel Haswell processors. A local attacker could use this to cause a denial of     service (system crash). (CVE-2021-28971)

    It was discovered that the RPA PCI Hotplug driver implementation in the Linux kernel did not properly     handle device name writes via sysfs, leading to a buffer overflow. A privileged attacker could use this to     cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2021-28972)

    It was discovered that the Freescale Gianfar Ethernet driver for the Linux kernel did not properly handle     receive queue overrun when jumbo frames were enabled in some situations. An attacker could use this to     cause a denial of service (system crash). (CVE-2021-29264)

    It was discovered that the vDPA backend virtio driver in the Linux kernel contained a use-after-free     vulnerability. An attacker could use this to cause a denial of service (system crash) or possibly execute     arbitrary code. (CVE-2021-29266)

    It was discovered that the TIPC protocol implementation in the Linux kernel did not properly validate     passed encryption key sizes. A local attacker could use this to cause a denial of service (system crash).
    (CVE-2021-29646)

    It was discovered that the Qualcomm IPC router implementation in the Linux kernel did not properly     initialize memory passed to user space. A local attacker could use this to expose sensitive information     (kernel memory). (CVE-2021-29647)

    It was discovered that the BPF user mode driver implementation in the Linux kernel did not properly     deallocate memory in some situations. A local attacker could use this to cause a denial of service (memory     exhaustion). (CVE-2021-29649)

    It was discovered that a race condition existed in the netfilter subsystem of the Linux kernel when     replacing tables. A local attacker could use this to cause a denial of service (system crash).
    (CVE-2021-29650)

    Felix Wilhelm discovered that the KVM implementation in the Linux kernel for AMD processors contained race     conditions on nested VMCB controls. A local attacker in a guest vm could possibly use this to gain     elevated privileges. (CVE-2021-29657)

    Dan Carpenter discovered that the block device manager (dm) implementation in the Linux kernel contained a     buffer overflow in the ioctl for listing devices. A privileged local attacker could use this to cause a     denial of service (system crash). (CVE-2021-31916)

     discovered that the IEEE 1394 (Firewire) nosy packet sniffer driver in the Linux kernel did not     properly perform reference counting in some situations, leading to a use-after-free vulnerability. A local     attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code.
    (CVE-2021-3483)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Severity
223718	Linux Distros Unpatched Vulnerability : CVE-2021-29657	Nessus	Misc.	high
149407	Ubuntu 20.04 LTS : Linux kernel (OEM) vulnerabilities (USN-4948-1)	Nessus	Ubuntu Local Security Checks	high

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CVE-2021-29657

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