An issue was discovered in Xen through 4.13.x, allowing x86 HVM guest OS users to cause a hypervisor crash. An inverted conditional in x86 HVM guests' dirty video RAM tracking code allows such guests to make Xen de-reference a pointer guaranteed to point at unmapped space. A malicious or buggy HVM guest may cause the hypervisor to crash, resulting in Denial of Service (DoS) affecting the entire host. Xen versions from 4.8 onwards are affected. Xen versions 4.7 and earlier are not affected. Only x86 systems are affected. Arm systems are not affected. Only x86 HVM guests using shadow paging can leverage the vulnerability. In addition, there needs to be an entity actively monitoring a guest's video frame buffer (typically for display purposes) in order for such a guest to be able to leverage the vulnerability. x86 PV guests, as well as x86 HVM guests using hardware assisted paging (HAP), cannot leverage the vulnerability.

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 x86 HVM guest OS users to cause a hypervisor crash. An inverted conditional in x86 HVM guests' dirty video RAM tracking code allows such guests to make Xen de-reference a pointer guaranteed to point at unmapped space. A malicious or buggy HVM guest may cause the hypervisor to crash, resulting in Denial of Service (DoS) affecting the entire host.
Xen versions from 4.8 onwards are affected. Xen versions 4.7 and earlier are not affected. Only x86 systems are affected. Arm systems are not affected. Only x86 HVM guests using shadow paging can leverage the vulnerability. In addition, there needs to be an entity actively monitoring a guest's video frame buffer (typically for display purposes) in order for such a guest to be able to leverage the vulnerability. x86 PV guests, as well as x86 HVM guests using hardware assisted paging (HAP), cannot leverage the vulnerability.

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.

This update for xen fixes the following issues :

  - CVE-2020-15563: Fixed inverted code paths in x86 dirty     VRAM tracking (bsc#1173377).

  - CVE-2020-15565: Fixed insufficient cache write-back     under VT-d (bsc#1173378).

  - CVE-2020-15566: Fixed incorrect error handling in event     channel port allocation (bsc#1173376).

  - CVE-2020-15567: Fixed non-atomic modification of live     EPT PTE (bsc#1173380).

  - CVE-2020-0543: Special Register Buffer Data Sampling     (SRBDS) aka 'CrossTalk' (bsc#1172205).

Additional upstream bug fixes (bsc#1027519)

This update was imported from the SUSE:SLE-15-SP2:Update update project.

This update for xen fixes the following issues :

  - CVE-2020-15563: Fixed inverted code paths in x86 dirty     VRAM tracking (bsc#1173377).

  - CVE-2020-15565: Fixed insufficient cache write-back     under VT-d (bsc#1173378).

  - CVE-2020-15566: Fixed incorrect error handling in event     channel port allocation (bsc#1173376).

  - CVE-2020-15567: Fixed non-atomic modification of live     EPT PTE (bsc#1173380).

  - CVE-2020-0543: Special Register Buffer Data Sampling     (SRBDS) aka 'CrossTalk' (bsc#1172205).

Additional upstream bug fixes (bsc#1027519)

This update was imported from the SUSE:SLE-15-SP1:Update update project.

This update for xen fixes the following issues :

CVE-2020-15563: Fixed inverted code paths in x86 dirty VRAM tracking (bsc#1173377).

CVE-2020-15565: Fixed insufficient cache write-back under VT-d (bsc#1173378).

CVE-2020-15566: Fixed incorrect error handling in event channel port allocation (bsc#1173376).

CVE-2020-15567: Fixed non-atomic modification of live EPT PTE (bsc#1173380).

CVE-2020-0543: Special Register Buffer Data Sampling (SRBDS) aka 'CrossTalk' (bsc#1172205).

Additional upstream bug fixes (bsc#1027519)

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

This update for xen fixes the following issues :

CVE-2020-15563: Fixed inverted code paths in x86 dirty VRAM tracking (bsc#1173377).

CVE-2020-15565: Fixed insufficient cache write-back under VT-d (bsc#1173378).

CVE-2020-15566: Fixed incorrect error handling in event channel port allocation (bsc#1173376).

CVE-2020-15567: Fixed non-atomic modification of live EPT PTE (bsc#1173380).

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

This update for xen fixes the following issues :

CVE-2020-15563: Fixed inverted code paths in x86 dirty VRAM tracking (bsc#1173377).

CVE-2020-15565: Fixed insufficient cache write-back under VT-d (bsc#1173378).

CVE-2020-15567: Fixed non-atomic modification of live EPT PTE (bsc#1173380).

Note that Tenable Network Security has extracted the preceding description block directly from the SUSE security advisory. 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
165248	Ubuntu 20.04 LTS : Xen vulnerabilities (USN-5617-1)	Nessus	Ubuntu Local Security Checks	high
149087	Xen Inverted Conditional DoS (XSA-319)	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
138749	openSUSE Security Update : xen (openSUSE-2020-985)	Nessus	SuSE Local Security Checks	high
138741	openSUSE Security Update : xen (openSUSE-2020-965)	Nessus	SuSE Local Security Checks	high
138535	Fedora 32 : xen (2020-fbc13516af)	Nessus	Fedora Local Security Checks	high
138495	SUSE SLED15 / SLES15 Security Update : xen (SUSE-SU-2020:1902-1)	Nessus	SuSE Local Security Checks	high
138492	SUSE SLES12 Security Update : xen (SUSE-SU-2020:1891-1)	Nessus	SuSE Local Security Checks	high
138434	SUSE SLED15 / SLES15 Security Update : xen (SUSE-SU-2020:1889-1)	Nessus	SuSE Local Security Checks	high
138433	SUSE SLES12 Security Update : xen (SUSE-SU-2020:1887-1)	Nessus	SuSE Local Security Checks	high
138432	SUSE SLES12 Security Update : xen (SUSE-SU-2020:1886-1)	Nessus	SuSE Local Security Checks	high
138394	Debian DSA-4723-1 : xen - security update	Nessus	Debian Local Security Checks	high

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