CVE-2020-11739 | Date: (C)2020-04-14 (M)2024-02-22 |
An issue was discovered in Xen through 4.13.x, allowing guest OS users to cause a denial of service or possibly gain privileges because of missing memory barriers in read-write unlock paths. The read-write unlock paths don't contain a memory barrier. On Arm, this means a processor is allowed to re-order the memory access with the preceding ones. In other words, the unlock may be seen by another processor before all the memory accesses within the "critical" section. As a consequence, it may be possible to have a writer executing a critical section at the same time as readers or another writer. In other words, many of the assumptions (e.g., a variable cannot be modified after a check) in the critical sections are not safe anymore. The read-write locks are used in hypercalls (such as grant-table ones), so a malicious guest could exploit the race. For instance, there is a small window where Xen can leak memory if XENMAPSPACE_grant_table is used concurrently. A malicious guest may be able to leak memory, or cause a hypervisor crash resulting in a Denial of Service (DoS). Information leak and privilege escalation cannot be excluded.
CVSS Score and Metrics +CVSS Score and Metrics -CVSS V3 Severity: | CVSS V2 Severity: |
CVSS Score : 7.8 | CVSS Score : 6.9 |
Exploit Score: 1.1 | Exploit Score: 3.4 |
Impact Score: 6.0 | Impact Score: 10.0 |
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CVSS V3 Metrics: | CVSS V2 Metrics: |
Attack Vector: LOCAL | Access Vector: LOCAL |
Attack Complexity: HIGH | Access Complexity: MEDIUM |
Privileges Required: LOW | Authentication: NONE |
User Interaction: NONE | Confidentiality: COMPLETE |
Scope: CHANGED | Integrity: COMPLETE |
Confidentiality: HIGH | Availability: COMPLETE |
Integrity: HIGH | |
Availability: HIGH | |
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