HighFix available
xen — security advisory
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.
- Products
- xen
- Affected versions
- Not specified
- Fixed versions
- 4.10.4-r3, 4.11.3-r2, 4.12.2-r1, 4.13.0-r1, 4.13.0-r3
- CVEs
- CVE-2020-11739
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 12:01 UTC · Revision 1
Source evidence
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.
osv:ALPINE-CVE-2020-11739
xen
Fixed versions: 4.12.2-r1
xen
Fixed versions: 4.13.0-r1
xen
Fixed versions: 4.13.0-r3
xen
Fixed versions: 4.13.0-r3
xen
Fixed versions: 4.13.0-r3
xen
Fixed versions: 4.13.0-r3
xen
Fixed versions: 4.13.0-r3
xen
Fixed versions: 4.13.0-r3
xen
Fixed versions: 4.13.0-r3
xen
Fixed versions: 4.13.0-r3
xen
Fixed versions: 4.13.0-r3
xen
Fixed versions: 4.13.0-r3
xen
Fixed versions: 4.13.0-r3
xen
Fixed versions: 4.13.0-r3
xen
Fixed versions: 4.13.0-r3
xen
Fixed versions: 4.10.4-r3
xen
Fixed versions: 4.11.3-r2
Complete source record
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"method": "structured",
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],
"modified": "2026-10-26T11:17:55.100397376Z",
"provider": "osv",
"upstream": [
"CVE-2020-11739"
],
"references": [
"https://security.alpinelinux.org/vuln/CVE-2020-11739"
]
},
"related_cves": [
{
"value": "CVE-2020-11739",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 450352,
"published_at": "2020-04-14T13:15:12.703+00:00"
}