Race condition in xen (Alpine package)

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 update from vendor's website.

Vulnerable software versions

xen (Alpine package): 4.1.3-r0 - 4.12.3-r1

External links

http://git.alpinelinux.org/aports/commit/?id=3992359a2b257143f6d354a15e0d3b338c5d8e45
http://git.alpinelinux.org/aports/commit/?id=4eb93417705cbc9cb434bae5e88502bf944f7652
http://git.alpinelinux.org/aports/commit/?id=054ec5f5456be1d95d13e7b5c5607e9c0ed5904d
http://git.alpinelinux.org/aports/commit/?id=a95c3541d2bc3ba65df7c81a62b776d2fd0ed4ce
http://git.alpinelinux.org/aports/commit/?id=fc28a340a4fd7b262e11f636ab2fafe24e2d05a2

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.