UBUNTU-CVE-2021-26933 (CVE-2021-26933)
Vulnerability from osv_ubuntu – Published: 2021-02-17 02:15 – Updated: 2026-05-20 14:53 – Source websiteAn issue was discovered in Xen 4.9 through 4.14.x. On Arm, a guest is allowed to control whether memory accesses are bypassing the cache. This means that Xen needs to ensure that all writes (such as the ones during scrubbing) have reached the memory before handing over the page to a guest. Unfortunately, the operation to clean the cache is happening before checking if the page was scrubbed. Therefore there is no guarantee when all the writes will reach the memory.
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{
"binary_name": "xenstore-utils",
"binary_version": "4.20.2+7-g1badcf5035-2build2"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "xen",
"purl": "pkg:deb/ubuntu/xen@4.20.2+7-g1badcf5035-2build2?arch=source\u0026distro=resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"4.20.0+68-g35cb38b222-1",
"4.20.2+7-g1badcf5035-2",
"4.20.2+7-g1badcf5035-2build2"
]
}
],
"aliases": [],
"details": "An issue was discovered in Xen 4.9 through 4.14.x. On Arm, a guest is allowed to control whether memory accesses are bypassing the cache. This means that Xen needs to ensure that all writes (such as the ones during scrubbing) have reached the memory before handing over the page to a guest. Unfortunately, the operation to clean the cache is happening before checking if the page was scrubbed. Therefore there is no guarantee when all the writes will reach the memory.",
"id": "UBUNTU-CVE-2021-26933",
"modified": "2026-05-20T14:53:11Z",
"published": "2021-02-17T02:15:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2021-26933"
},
{
"type": "REPORT",
"url": "https://www.openwall.com/lists/oss-security/2021/02/16/5"
},
{
"type": "REPORT",
"url": "https://xenbits.xen.org/xsa/advisory-364.html"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2021-26933"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2021-26933"
]
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.