An issue was discovered in Xen through 4.13.x, allowing Intel guest OS users to gain privileges or cause a denial of service because of non-atomic modification of a live EPT PTE. 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. A guest administrator or perhaps even an unprivileged guest user might be able to cause denial of service, data corruption, or privilege escalation. Only systems using Intel CPUs are vulnerable. Systems using AMD CPUs, and Arm systems, are not vulnerable. Only systems using nested paging (hap, aka nested paging, aka in this case Intel EPT) are vulnerable. Only HVM and PVH guests can exploit the vulnerability. The presence and scope of the vulnerability depends on the precise optimisations performed by the compiler used to build Xen. If the compiler generates (a) a single 64-bit write, or (b) a series of read-modify-write operations in the same order as the source code, the hypervisor is not vulnerable. For example, in one test build using GCC 8.3 with normal settings, the compiler generated multiple (unlocked) read-modify-write operations in source-code order, which did not constitute a vulnerability. We have not been able to survey compilers; consequently we cannot say which compiler(s) might produce vulnerable code (with which code-generation options). The source code clearly violates the C rules, and thus should be considered vulnerable.
Published 2020-07-07 13:15:10
Updated 2022-05-03 13:57:33
Source MITRE
View at NVD,   CVE.org
Vulnerability category: Gain privilegeDenial of service

Exploit prediction scoring system (EPSS) score for CVE-2020-15567

Probability of exploitation activity in the next 30 days: 0.05%

Percentile, the proportion of vulnerabilities that are scored at or less: ~ 12 % EPSS Score History EPSS FAQ

CVSS scores for CVE-2020-15567

Base Score Base Severity CVSS Vector Exploitability Score Impact Score Score Source
4.4
MEDIUM AV:L/AC:M/Au:N/C:P/I:P/A:P
3.4
6.4
NIST
7.8
HIGH CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
1.1
6.0
NIST

CWE ids for CVE-2020-15567

References for CVE-2020-15567

Products affected by CVE-2020-15567

This web site uses cookies for managing your session, storing preferences, website analytics and additional purposes described in our privacy policy.
By using this web site you are agreeing to CVEdetails.com terms of use!