CVE-2020-15567 Detail

Current Description

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.


View Analysis Description

Severity



CVSS 3.x Severity and Metrics:

NIST CVSS score
NIST: NVD
Base Score:  7.8 HIGH
Vector:  CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H


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Note: NVD Analysts have published a CVSS score for this CVE based on publicly available information at the time of analysis. The CNA has not provided a score within the CVE List.

References to Advisories, Solutions, and Tools

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Hyperlink Resource
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00024.html
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00031.html
http://www.openwall.com/lists/oss-security/2020/07/07/6 Mailing List  Third Party Advisory 
http://xenbits.xen.org/xsa/advisory-328.html Mitigation  Patch  Vendor Advisory 
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/MXESCOVI7AVRNC7HEAMFM7PMEO6D3AUH/
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/VB3QJJZV23Z2IDYEMIHELWYSQBUEW6JP/
https://security.gentoo.org/glsa/202007-02
https://www.debian.org/security/2020/dsa-4723 Third Party Advisory 

Weakness Enumeration

CWE-ID CWE Name Source
CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') cwe source acceptance level NIST  
CWE-269 Improper Privilege Management cwe source acceptance level NIST  

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Change History

9 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2020-15567
NVD Published Date:
07/07/2020
NVD Last Modified:
07/26/2020
Source:
MITRE