qemu — security advisory
A flaw was found in the QXL display device emulation in QEMU. A double fetch of guest controlled values `cursor->header.width` and `cursor->header.height` can lead to the allocation of a small cursor object followed by a subsequent heap-based buffer overflow. A malicious privileged guest user could use this flaw to crash the QEMU process on the host or potentially execute arbitrary code within the context of the QEMU process.
- Products
- qemu
- Affected versions
- Not specified
- Fixed versions
- 1:7.0+dfsg-1
- CVEs
- CVE-2021-4207
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 02:01 UTC · Revision 1
Source evidence
A flaw was found in the QXL display device emulation in QEMU. A double fetch of guest controlled values `cursor->header.width` and `cursor->header.height` can lead to the allocation of a small cursor object followed by a subsequent heap-based buffer overflow. A malicious privileged guest user could use this flaw to crash the QEMU process on the host or potentially execute arbitrary code within the context of the QEMU process.
osv:DEBIAN-CVE-2021-4207
qemu
Fixed versions: 1:7.0+dfsg-1
qemu
Fixed versions: 1:7.0+dfsg-1
qemu
Fixed versions: 1:7.0+dfsg-1
Complete source record
{
"id": "c790c0082b5556d13f4c0dac10074e6cb600bf2dc919e6a823f797b3f8bd68aa",
"url": "https://osv.dev/vulnerability/DEBIAN-CVE-2021-4207",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "DEBIAN-CVE-2021-4207",
"summary": "A flaw was found in the QXL display device emulation in QEMU. A double fetch of guest controlled values `cursor->header.width` and `cursor->header.height` can lead to the allocation of a small cursor object followed by a subsequent heap-based buffer overflow. A malicious privileged guest user could use this flaw to crash the QEMU process on the host or potentially execute arbitrary code within the context of the QEMU process.",
"evidence": "osv:DEBIAN-CVE-2021-4207",
"products": [
{
"name": {
"value": "qemu",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "1:7.0+dfsg-1",
"evidence": "/affected/0/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "qemu",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "1:7.0+dfsg-1",
"evidence": "/affected/1/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "qemu",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "1:7.0+dfsg-1",
"evidence": "/affected/2/ranges"
}
],
"affected_versions": []
}
],
"severity": "high",
"structured": {
"id": "DEBIAN-CVE-2021-4207",
"aliases": [
"DEBIAN-CVE-2021-4207"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1:7.0+dfsg-1"
}
]
}
],
"package": {
"name": "qemu",
"purl": "pkg:deb/debian/qemu?arch=source&distro=bookworm",
"ecosystem": "Debian:12"
},
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2021-4207.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1:7.0+dfsg-1"
}
]
}
],
"package": {
"name": "qemu",
"purl": "pkg:deb/debian/qemu?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2021-4207.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1:7.0+dfsg-1"
}
]
}
],
"package": {
"name": "qemu",
"purl": "pkg:deb/debian/qemu?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2021-4207.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
],
"modified": "2026-10-23T18:05:23.128378735Z",
"provider": "osv",
"upstream": [
"CVE-2021-4207"
],
"references": [
"https://security-tracker.debian.org/tracker/CVE-2021-4207"
]
},
"related_cves": [
{
"value": "CVE-2021-4207",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 424382,
"published_at": "2022-04-29T17:15:20.1+00:00"
}