Multiple vulnerabilities in Xen

Published: 2020-07-09

Risk	Medium
Patch available	YES
Number of vulnerabilities	5
CVE-ID	CVE-2020-15567 CVE-2020-15564 CVE-2020-15565 CVE-2020-15563 CVE-2020-15566
CWE-ID	CWE-362 CWE-399 CWE-264 CWE-822
Exploitation vector	Local network
Public exploit	Public exploit code for vulnerability #1 is available. Public exploit code for vulnerability #2 is available. Public exploit code for vulnerability #3 is available. Public exploit code for vulnerability #4 is available. Public exploit code for vulnerability #5 is available.
Vulnerable software Subscribe	Xen Server applications / Virtualization software
Vendor	Xen Project

Security Bulletin

This security bulletin contains information about 5 vulnerabilities.

1) Race condition

EUVDB-ID: #VU29598

Risk: Medium

CVSSv3.1: 7.2 [CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H/E:P/RL:O/RC:C]

CVE-ID: CVE-2020-15567

CWE-ID: CWE-362 - Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

Exploit availability: No

Description

The vulnerability allows a remote attacker to escalate privileges on the system.

The vulnerability exists due to improper management of internal resources in Xen. When mapping guest EPT (nested paging) tables, Xen would in some circumstances use a series of non-atomic bitfield writes. Depending on the compiler version and optimisation flags, Xen might expose a dangerous partially written PTE to the hardware, which an attacker might be able to race to exploit. An attacker with access to guest operating system can perform a denial of service (DoS) attack or escalate privileges on the host operating system.

Note: the vulnerability can be exploited only on systems with Intel processors.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Xen: 4.0.0 - 4.13.1

External links

http://www.openwall.com/lists/oss-security/2020/07/07/6
http://xenbits.xen.org/xsa/advisory-328.html

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the local network (LAN).

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.

2) Resource management error

EUVDB-ID: #VU29599

Risk: Low

CVSSv3.1: 4.9 [CVSS:3.1/AV:A/AC:H/PR:H/UI:N/S:C/C:N/I:N/A:H/E:P/RL:O/RC:C]

CVE-ID: CVE-2020-15564

CWE-ID: CWE-399 - Resource Management Errors

Exploit availability: No

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to missing alignment check in VCPUOP_register_vcpu_info hypercall in Xen. A attacker with privileged access to guest operating system can crash the hypervisor.

Note: the vulnerability affects Arm systems only.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Xen: 4.0.0 - 4.13.1

External links

http://www.openwall.com/lists/oss-security/2020/07/07/5
http://xenbits.xen.org/xsa/advisory-327.html

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated privileged user via the local network (LAN).

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.

3) Permissions, Privileges, and Access Controls

EUVDB-ID: #VU29600

Risk: Medium

CVSSv3.1: 7.2 [CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H/E:P/RL:O/RC:C]

CVE-ID: CVE-2020-15565

CWE-ID: CWE-264 - Permissions, Privileges, and Access Controls

Exploit availability: No

Description

The vulnerability allows a remote attacker to escalate privileges on the system or perform a denial of service attack.

The vulnerability exists due to application does not properly impose security restrictions. When page tables are shared between IOMMU and CPU, changes to them require flushing of both TLBs. Furthermore, IOMMUs may be non-coherent, and hence prior to flushing IOMMU TLBs, a CPU cache also needs writing back to memory after changes were made. Such writing back of cached data was missing in particular when splitting large page mappings into smaller granularity ones. A malicious guest may be able to retain read/write DMA access to frames returned to Xen's free pool, and later reused for another purpose.

Successful exploitation of the vulnerability may allows privileges escalation on the host operating system.

Note: the vulnerability affects Intel x86 systems only.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Xen: 3.2 - 4.13.1

External links

http://www.openwall.com/lists/oss-security/2020/07/07/4
http://xenbits.xen.org/xsa/advisory-321.html

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the local network (LAN).

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.

4) Untrusted Pointer Dereference

EUVDB-ID: #VU29601

Risk: Medium

CVSSv3.1: 5.2 [CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:C/C:N/I:N/A:H/E:P/RL:O/RC:C]

CVE-ID: CVE-2020-15563

CWE-ID: CWE-822 - Untrusted Pointer Dereference

Exploit availability: No

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to inverted code paths in x86 dirty VRAM tracking in Xen. An attacker with access to HVM guest operating system can crash the hypervisor.

Note: the vulnerability affects x86 systems only.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Xen: 4.8.0 - 4.13.1

External links

http://www.openwall.com/lists/oss-security/2020/07/07/3
http://xenbits.xen.org/xsa/advisory-319.html

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the local network (LAN).

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.

5) Resource management error

EUVDB-ID: #VU29602

Risk: Low

CVSSv3.1: 6.1 [CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H/E:P/RL:O/RC:C]

CVE-ID: CVE-2020-15566

CWE-ID: CWE-399 - Resource Management Errors

Exploit availability: No

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to improper error handling in event-channel port allocation in Xen. An attacker with access to guest operating system can consume more than 1023 event channels and crash the hypervisor.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Xen: 4.10.0 - 4.13.1

External links

http://www.openwall.com/lists/oss-security/2020/07/07/2
http://xenbits.xen.org/xsa/advisory-317.html

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the local network (LAN).

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.