An issue was discovered in Xen through 4.13.x, allowing Arm guest OS users to cause a hypervisor crash because of a missing alignment check in VCPUOP_register_vcpu_info. The hypercall VCPUOP_register_vcpu_info is used by a guest to register a shared region with the hypervisor. The region will be mapped into Xen address space so it can be directly accessed. On Arm, the region is accessed with instructions that require a specific alignment. Unfortunately, there is no check that the address provided by the guest will be correctly aligned. As a result, a malicious guest could cause a hypervisor crash by passing a misaligned address. A malicious guest administrator may cause a hypervisor crash, resulting in a Denial of Service (DoS). All Xen versions are vulnerable. Only Arm systems are vulnerable. x86 systems are not affected.

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

  - An issue was discovered in Xen through 4.13.x, allowing Arm guest OS users to cause a hypervisor crash     because of a missing alignment check in VCPUOP_register_vcpu_info. The hypercall VCPUOP_register_vcpu_info     is used by a guest to register a shared region with the hypervisor. The region will be mapped into Xen     address space so it can be directly accessed. On Arm, the region is accessed with instructions that     require a specific alignment. Unfortunately, there is no check that the address provided by the guest will     be correctly aligned. As a result, a malicious guest could cause a hypervisor crash by passing a     misaligned address. A malicious guest administrator may cause a hypervisor crash, resulting in a Denial of     Service (DoS). All Xen versions are vulnerable. Only Arm systems are vulnerable. x86 systems are not     affected. (CVE-2020-15564)

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

The remote Ubuntu 20.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-5617-1 advisory.

    It was discovered that memory contents previously stored in microarchitectural special registers after     RDRAND, RDSEED, and SGX EGETKEY read operations on Intel client and Xeon E3 processors may be briefly     exposed to processes on the same or different processor cores. A local attacker could use this to expose     sensitive information. (CVE-2020-0543)

    Julien Grall discovered that Xen incorrectly handled memory barriers on ARM-based systems. An attacker     could possibly use this issue to cause a denial of service, obtain sensitive information or escalate     privileges. (CVE-2020-11739)

    Ilja Van Sprundel discovered that Xen incorrectly handled profiling of guests. An unprivileged attacker     could use this issue to obtain sensitive information from other guests, cause a denial of service or     possibly gain privileges. (CVE-2020-11740, CVE-2020-11741)

    It was discovered that Xen incorrectly handled grant tables. A malicious guest could possibly use this     issue to cause a denial of service. (CVE-2020-11742, CVE-2020-11743)

    Jan Beulich discovered that Xen incorrectly handled certain code paths. An attacker could possibly use     this issue to cause a denial of service. (CVE-2020-15563)

    Julien Grall discovered that Xen incorrectly verified memory addresses provided by the guest on ARM-based     systems. A malicious guest administrator could possibly use this issue to cause a denial of service.
    (CVE-2020-15564)

    Roger Pau Monn discovered that Xen incorrectly handled caching on x86 Intel systems. An attacker could     possibly use this issue to cause a denial of service. (CVE-2020-15565)

    It was discovered that Xen incorrectly handled error in event-channel port allocation. A malicious guest     could possibly use this issue to cause a denial of service. (CVE-2020-15566)

    Jan Beulich discovered that Xen incorrectly handled certain EPT (Extended Page Tables).

    An attacker could possibly use this issue to cause a denial of service, data corruption or privilege     escalation. (CVE-2020-15567)

    Andrew Cooper discovered that Xen incorrectly handled PCI passthrough. An attacker could possibly use this     issue to cause a denial of service. (CVE-2020-25595)

    Andrew Cooper discovered that Xen incorrectly sanitized path injections. An attacker could possibly use     this issue to cause a denial of service. (CVE-2020-25596)

    Jan Beulich discovered that Xen incorrectly handled validation of event channels. An attacker could     possibly use this issue to cause a denial of service. (CVE-2020-25597)

    Julien Grall and Jan Beulich discovered that Xen incorrectly handled resetting event channels. An attacker     could possibly use this issue to cause a denial of service or obtain sensitive information.
    (CVE-2020-25599)

    Julien Grall discovered that Xen incorrectly handled event channels memory allocation on 32-bits domains.
    An attacker could possibly use this issue to cause a denial of service. (CVE-2020-25600)

    Jan Beulich discovered that Xen incorrectly handled resetting or cleaning up event channels. An attacker     could possibly use this issue to cause a denial of service. (CVE-2020-25601)

    Andrew Cooper discovered that Xen incorrectly handled certain Intel specific MSR (Model Specific     Registers). An attacker could possibly use this issue to cause a denial of service. (CVE-2020-25602)

    Julien Grall discovered that Xen incorrectly handled accessing/allocating event channels. An attacker     could possibly use this issue to cause a denial of service, obtain sensitive information of privilege     escalation. (CVE-2020-25603)

    Igor Druzhinin discovered that Xen incorrectly handled locks. An attacker could possibly use this issue to     cause a denial of service. (CVE-2020-25604)

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.

According to its self-reported version number, the Xen hypervisor installed on the remote host is affected by an issue allowing Arm guest OS users to cause a hypervisor crash because of a missing alignment check in VCPUOP_register_vcpu_info. The hypercall VCPUOP_register_vcpu_info is used by a guest to register a shared region with the hypervisor. The region will be mapped into Xen address space so it can be directly accessed. On Arm, the region is accessed with instructions that require a specific alignment. Unfortunately, there is no check that the address provided by the guest will be correctly aligned. As a result, a malicious guest could cause a hypervisor crash by passing a misaligned address. A malicious guest administrator may cause a hypervisor crash, resulting in a Denial of Service (DoS). All Xen versions are vulnerable. Only Arm systems are vulnerable. x86 systems are not affected.

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

The remote host is affected by the vulnerability described in GLSA-202007-02 (Xen: Multiple vulnerabilities)

    Multiple vulnerabilities have been discovered in Xen. Please review the       CVE identifiers referenced below for details.
  Impact :

    Please review the referenced CVE identifiers for details.
  Workaround :

    There is no known workaround at this time.

incorrect error handling in event channel port allocation leads to DoS [XSA-317, CVE-2020-15566] (#1854465) inverted code paths in x86 dirty VRAM tracking leads to DoS [XSA-319, CVE-2020-15563] (#1854463) xen:
insufficient cache write-back under VT-d leads to DoS [XSA-321, CVE-2020-15565] (#1854467) missing alignment check in VCPUOP_register_vcpu_info leads to DoS [XSA-327, CVE-2020-15564] (#1854458) non-atomic modification of live EPT PTE leads to DoS [XSA-328, CVE-2020-15567] (#1854464)

Note that Tenable Network Security has extracted the preceding description block directly from the Fedora update system website.
Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

Multiple vulnerabilities have been discovered in the Xen hypervisor, which could result in denial of service, guest-to-host privilege escalation or information leaks.

ID	Name	Product	Family	Severity
257512	Linux Distros Unpatched Vulnerability : CVE-2020-15564	Nessus	Misc.	medium
165248	Ubuntu 20.04 LTS : Xen vulnerabilities (USN-5617-1)	Nessus	Ubuntu Local Security Checks	high
149066	Xen Missing Alignment Check DoS (XSA-327)	Nessus	Misc.	medium
138925	GLSA-202007-02 : Xen: Multiple vulnerabilities	Nessus	Gentoo Local Security Checks	high
138864	Fedora 31 : xen (2020-76cf2b0f0a)	Nessus	Fedora Local Security Checks	high
138535	Fedora 32 : xen (2020-fbc13516af)	Nessus	Fedora Local Security Checks	high
138394	Debian DSA-4723-1 : xen - security update	Nessus	Debian Local Security Checks	high

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