MediumFix available
squid, squid3 — security advisory
An issue was discovered in Squid before 4.15 and 5.x before 5.0.6. Due to a memory-management bug, it is vulnerable to a Denial of Service attack (against all clients using the proxy) via HTTP Range request processing.
- Products
- squid, squid3
- Affected versions
- 3.3.8-1ubuntu16, 3.3.8-1ubuntu17, 3.5.12-1ubuntu6, 3.5.12-1ubuntu7, 3.5.12-1ubuntu7.1, 3.5.12-1ubuntu7.10, 3.5.12-1ubuntu7.11, 3.5.12-1ubuntu7.12, 3.5.12-1ubuntu7.13, 3.5.12-1ubuntu7.14, 3.5.12-1ubuntu7.15, 3.5.12-1ubuntu7.16, 3.5.12-1ubuntu7.16+esm1, 3.5.12-1ubuntu7.16+esm2, 3.5.12-1ubuntu7.16+esm3, 3.5.12-1ubuntu7.16+esm4, 3.5.12-1ubuntu7.16+esm5, 3.5.12-1ubuntu7.16+esm6, 3.5.12-1ubuntu7.16+esm7, 3.5.12-1ubuntu7.2, 3.5.12-1ubuntu7.3, 3.5.12-1ubuntu7.4, 3.5.12-1ubuntu7.5, 3.5.12-1ubuntu7.6, 3.5.12-1ubuntu7.7, 3.5.12-1ubuntu7.8, 3.5.12-1ubuntu7.9, 3.5.23-5ubuntu1, 3.5.23-5ubuntu2, 3.5.27-1ubuntu1, 3.5.27-1ubuntu1.1, 3.5.27-1ubuntu1.10, 3.5.27-1ubuntu1.2, 3.5.27-1ubuntu1.3, 3.5.27-1ubuntu1.4, 3.5.27-1ubuntu1.5, 3.5.27-1ubuntu1.6, 3.5.27-1ubuntu1.7, 3.5.27-1ubuntu1.8, 3.5.27-1ubuntu1.9, 4.10-1ubuntu1, 4.10-1ubuntu1.1, 4.10-1ubuntu1.2, 4.10-1ubuntu1.3, 4.8-1ubuntu2, 4.8-1ubuntu3, 4.9-2ubuntu1, 4.9-2ubuntu2, 4.9-2ubuntu3, 4.9-2ubuntu4
- Fixed versions
- 3.5.27-1ubuntu1.11, 4.10-1ubuntu1.4
- CVEs
- CVE-2021-31806
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 13:03 UTC · Revision 1
Source evidence
An issue was discovered in Squid before 4.15 and 5.x before 5.0.6. Due to a memory-management bug, it is vulnerable to a Denial of Service attack (against all clients using the proxy) via HTTP Range request processing.
osv:UBUNTU-CVE-2021-31806
squid3
Fixed versions: Not specified
squid3
Fixed versions: 3.5.27-1ubuntu1.11
squid
Fixed versions: 4.10-1ubuntu1.4
Complete source record
{
"id": "c2e3e50d8c4722e26764885c5b0b184a1efe4dce539713751ec33c52abd9d20d",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2021-31806",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2021-31806",
"summary": "An issue was discovered in Squid before 4.15 and 5.x before 5.0.6. Due to a memory-management bug, it is vulnerable to a Denial of Service attack (against all clients using the proxy) via HTTP Range request processing.",
"evidence": "osv:UBUNTU-CVE-2021-31806",
"products": [
{
"name": {
"value": "squid3",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "3.3.8-1ubuntu16",
"evidence": "/affected/0/versions"
},
{
"value": "3.3.8-1ubuntu17",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu6",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.1",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.2",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.3",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.4",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.5",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.6",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.7",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.8",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.9",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.10",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.11",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.12",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.13",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.14",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.15",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.16",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.16+esm1",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.16+esm2",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.16+esm3",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.16+esm4",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.16+esm5",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.16+esm6",
"evidence": "/affected/0/versions"
},
{
"value": "3.5.12-1ubuntu7.16+esm7",
"evidence": "/affected/0/versions"
}
]
},
{
"name": {
"value": "squid3",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "3.5.27-1ubuntu1.11",
"evidence": "/affected/1/ranges"
}
],
"affected_versions": [
{
"value": "3.5.23-5ubuntu1",
"evidence": "/affected/1/versions"
},
{
"value": "3.5.23-5ubuntu2",
"evidence": "/affected/1/versions"
},
{
"value": "3.5.27-1ubuntu1",
"evidence": "/affected/1/versions"
},
{
"value": "3.5.27-1ubuntu1.1",
"evidence": "/affected/1/versions"
},
{
"value": "3.5.27-1ubuntu1.2",
"evidence": "/affected/1/versions"
},
{
"value": "3.5.27-1ubuntu1.3",
"evidence": "/affected/1/versions"
},
{
"value": "3.5.27-1ubuntu1.4",
"evidence": "/affected/1/versions"
},
{
"value": "3.5.27-1ubuntu1.5",
"evidence": "/affected/1/versions"
},
{
"value": "3.5.27-1ubuntu1.6",
"evidence": "/affected/1/versions"
},
{
"value": "3.5.27-1ubuntu1.7",
"evidence": "/affected/1/versions"
},
{
"value": "3.5.27-1ubuntu1.8",
"evidence": "/affected/1/versions"
},
{
"value": "3.5.27-1ubuntu1.9",
"evidence": "/affected/1/versions"
},
{
"value": "3.5.27-1ubuntu1.10",
"evidence": "/affected/1/versions"
}
]
},
{
"name": {
"value": "squid",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "4.10-1ubuntu1.4",
"evidence": "/affected/2/ranges"
}
],
"affected_versions": [
{
"value": "4.8-1ubuntu2",
"evidence": "/affected/2/versions"
},
{
"value": "4.8-1ubuntu3",
"evidence": "/affected/2/versions"
},
{
"value": "4.9-2ubuntu1",
"evidence": "/affected/2/versions"
},
{
"value": "4.9-2ubuntu2",
"evidence": "/affected/2/versions"
},
{
"value": "4.9-2ubuntu3",
"evidence": "/affected/2/versions"
},
{
"value": "4.9-2ubuntu4",
"evidence": "/affected/2/versions"
},
{
"value": "4.10-1ubuntu1",
"evidence": "/affected/2/versions"
},
{
"value": "4.10-1ubuntu1.1",
"evidence": "/affected/2/versions"
},
{
"value": "4.10-1ubuntu1.2",
"evidence": "/affected/2/versions"
},
{
"value": "4.10-1ubuntu1.3",
"evidence": "/affected/2/versions"
}
]
}
],
"severity": "medium",
"structured": {
"id": "UBUNTU-CVE-2021-31806",
"aliases": [
"UBUNTU-CVE-2021-31806"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
},
{
"type": "Ubuntu",
"score": "medium"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "squid3",
"purl": "pkg:deb/ubuntu/squid3?arch=source&distro=esm-infra-legacy%2Fxenial",
"ecosystem": "Ubuntu:Pro:16.04:LTS"
},
"versions": [
"3.3.8-1ubuntu16",
"3.3.8-1ubuntu17",
"3.5.12-1ubuntu6",
"3.5.12-1ubuntu7",
"3.5.12-1ubuntu7.1",
"3.5.12-1ubuntu7.2",
"3.5.12-1ubuntu7.3",
"3.5.12-1ubuntu7.4",
"3.5.12-1ubuntu7.5",
"3.5.12-1ubuntu7.6",
"3.5.12-1ubuntu7.7",
"3.5.12-1ubuntu7.8",
"3.5.12-1ubuntu7.9",
"3.5.12-1ubuntu7.10",
"3.5.12-1ubuntu7.11",
"3.5.12-1ubuntu7.12",
"3.5.12-1ubuntu7.13",
"3.5.12-1ubuntu7.14",
"3.5.12-1ubuntu7.15",
"3.5.12-1ubuntu7.16",
"3.5.12-1ubuntu7.16+esm1",
"3.5.12-1ubuntu7.16+esm2",
"3.5.12-1ubuntu7.16+esm3",
"3.5.12-1ubuntu7.16+esm4",
"3.5.12-1ubuntu7.16+esm5",
"3.5.12-1ubuntu7.16+esm6",
"3.5.12-1ubuntu7.16+esm7"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-31806.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "squid",
"binary_version": "3.5.12-1ubuntu7.16+esm7"
},
{
"binary_name": "squid-cgi",
"binary_version": "3.5.12-1ubuntu7.16+esm7"
},
{
"binary_name": "squid-common",
"binary_version": "3.5.12-1ubuntu7.16+esm7"
},
{
"binary_name": "squid-purge",
"binary_version": "3.5.12-1ubuntu7.16+esm7"
},
{
"binary_name": "squid3",
"binary_version": "3.5.12-1ubuntu7.16+esm7"
},
{
"binary_name": "squidclient",
"binary_version": "3.5.12-1ubuntu7.16+esm7"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "3.5.27-1ubuntu1.11"
}
]
}
],
"package": {
"name": "squid3",
"purl": "pkg:deb/ubuntu/squid3?arch=source&distro=bionic",
"ecosystem": "Ubuntu:18.04:LTS"
},
"versions": [
"3.5.23-5ubuntu1",
"3.5.23-5ubuntu2",
"3.5.27-1ubuntu1",
"3.5.27-1ubuntu1.1",
"3.5.27-1ubuntu1.2",
"3.5.27-1ubuntu1.3",
"3.5.27-1ubuntu1.4",
"3.5.27-1ubuntu1.5",
"3.5.27-1ubuntu1.6",
"3.5.27-1ubuntu1.7",
"3.5.27-1ubuntu1.8",
"3.5.27-1ubuntu1.9",
"3.5.27-1ubuntu1.10"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-31806.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "squid",
"binary_version": "3.5.27-1ubuntu1.11"
},
{
"binary_name": "squid-cgi",
"binary_version": "3.5.27-1ubuntu1.11"
},
{
"binary_name": "squid-common",
"binary_version": "3.5.27-1ubuntu1.11"
},
{
"binary_name": "squid-purge",
"binary_version": "3.5.27-1ubuntu1.11"
},
{
"binary_name": "squid3",
"binary_version": "3.5.27-1ubuntu1.11"
},
{
"binary_name": "squidclient",
"binary_version": "3.5.27-1ubuntu1.11"
}
],
"availability": "No subscription required"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "4.10-1ubuntu1.4"
}
]
}
],
"package": {
"name": "squid",
"purl": "pkg:deb/ubuntu/squid?arch=source&distro=focal",
"ecosystem": "Ubuntu:20.04:LTS"
},
"versions": [
"4.8-1ubuntu2",
"4.8-1ubuntu3",
"4.9-2ubuntu1",
"4.9-2ubuntu2",
"4.9-2ubuntu3",
"4.9-2ubuntu4",
"4.10-1ubuntu1",
"4.10-1ubuntu1.1",
"4.10-1ubuntu1.2",
"4.10-1ubuntu1.3"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-31806.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "squid",
"binary_version": "4.10-1ubuntu1.4"
},
{
"binary_name": "squid-cgi",
"binary_version": "4.10-1ubuntu1.4"
},
{
"binary_name": "squid-common",
"binary_version": "4.10-1ubuntu1.4"
},
{
"binary_name": "squid-purge",
"binary_version": "4.10-1ubuntu1.4"
},
{
"binary_name": "squidclient",
"binary_version": "4.10-1ubuntu1.4"
}
],
"availability": "No subscription required"
}
}
],
"modified": "2026-10-20T16:45:57.359514794Z",
"provider": "osv",
"upstream": [
"CVE-2021-31806"
],
"references": [
"https://ubuntu.com/security/CVE-2021-31806",
"https://github.com/squid-cache/squid/security/advisories/GHSA-pxwq-f3qr-w2xf",
"https://ubuntu.com/security/notices/USN-4981-1",
"https://www.cve.org/CVERecord?id=CVE-2021-31806"
]
},
"related_cves": [
{
"value": "CVE-2021-31806",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 389769,
"published_at": "2021-05-27T13:15:00+00:00"
}