Privilege escalation in Xen

1) Incorrect default permissions

EUVDB-ID: #VU31970

Risk: Low

CVSSv3.1: 6.8 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2020-15852

CWE-ID: CWE-276 - Incorrect Default Permissions

Exploit availability: No

Description

The vulnerability allows a local user to escalate privileges on the system.

An issue was discovered in the Linux kernel 5.5 through 5.7.9, as used in Xen through 4.13.x for x86 PV guests. An attacker may be granted the I/O port permissions of an unrelated task. This occurs because tss_invalidate_io_bitmap mishandling causes a loss of synchronization between the I/O bitmaps of TSS and Xen. A remote user with access to the guest system can gain elevated privileges.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Xen: 4.13.0 - 4.13.1

External links

http://www.openwall.com/lists/oss-security/2020/07/21/2
http://xenbits.xen.org/xsa/advisory-329.html
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=cadfad870154e14f745ec845708bc17d166065f2
http://github.com/torvalds/linux/commit/cadfad870154e14f745ec845708bc17d166065f2

Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.