Vulnerability Details : CVE-2020-15567
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.
Vulnerability category: Gain privilegeDenial of service
Products affected by CVE-2020-15567
- cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
- cpe:2.3:o:xen:xen:*:*:*:*:*:*:*:*
- cpe:2.3:o:fedoraproject:fedora:31:*:*:*:*:*:*:*
- cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:*
- cpe:2.3:o:opensuse:leap:15.1:*:*:*:*:*:*:*
- cpe:2.3:o:opensuse:leap:15.2:*:*:*:*:*:*:*
Exploit prediction scoring system (EPSS) score for CVE-2020-15567
0.05%
Probability of exploitation activity in the next 30 days
EPSS Score History
~ 12 %
Percentile, the proportion of vulnerabilities that are scored at or less
CVSS scores for CVE-2020-15567
Base Score | Base Severity | CVSS Vector | Exploitability Score | Impact Score | Score Source | First Seen |
---|---|---|---|---|---|---|
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
-
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.Assigned by: nvd@nist.gov (Primary)
References for CVE-2020-15567
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http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00024.html
[security-announce] openSUSE-SU-2020:0965-1: important: Security updateMailing List;Third Party Advisory
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http://www.openwall.com/lists/oss-security/2020/07/07/6
oss-security - Xen Security Advisory 328 v3 (CVE-2020-15567) - non-atomic modification of live EPT PTEMailing List;Third Party Advisory
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https://security.gentoo.org/glsa/202007-02
Xen: Multiple vulnerabilities (GLSA 202007-02) — Gentoo securityThird Party Advisory
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https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/MXESCOVI7AVRNC7HEAMFM7PMEO6D3AUH/
[SECURITY] Fedora 31 Update: xen-4.12.3-3.fc31 - package-announce - Fedora Mailing-ListsMailing List;Third Party Advisory
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https://www.debian.org/security/2020/dsa-4723
Third Party Advisory
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https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/VB3QJJZV23Z2IDYEMIHELWYSQBUEW6JP/
[SECURITY] Fedora 32 Update: xen-4.13.1-4.fc32 - package-announce - Fedora Mailing-ListsMailing List;Third Party Advisory
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http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00031.html
[security-announce] openSUSE-SU-2020:0985-1: important: Security updateMailing List;Third Party Advisory
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http://xenbits.xen.org/xsa/advisory-328.html
XSA-328 - Xen Security AdvisoriesMitigation;Patch;Vendor Advisory
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