High
e2guardian — security advisory
e2guardian v5.4.x <= v5.4.3r is affected by missing SSL certificate validation in the SSL MITM engine. In standalone mode (i.e., acting as a proxy or a transparent proxy), with SSL MITM enabled, e2guardian, if built with OpenSSL v1.1.x, did not validate hostnames in certificates of the web servers that it connected to, and thus was itself vulnerable to MITM attacks.
- Products
- e2guardian
- Affected versions
- 3.4.0.3-2, 5.3.3-1, 5.3.4-1, 5.3.4-2, 5.3.5-1, 5.3.5-2, 5.3.5-2build1, 5.3.5-3, 5.3.5-4.1ubuntu1, 5.3.5-6ubuntu1, 5.3.5-6ubuntu2, 5.3.5-6ubuntu3, 5.5.7-1, 5.5.8-1, 5.5.9-2, 5.5.9-2ubuntu1
- Fixed versions
- Not specified
- CVEs
- CVE-2021-44273
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 00:39 UTC · Revision 1
Source evidence
e2guardian v5.4.x <= v5.4.3r is affected by missing SSL certificate validation in the SSL MITM engine. In standalone mode (i.e., acting as a proxy or a transparent proxy), with SSL MITM enabled, e2guardian, if built with OpenSSL v1.1.x, did not validate hostnames in certificates of the web servers that it connected to, and thus was itself vulnerable to MITM attacks.
osv:UBUNTU-CVE-2021-44273
e2guardian
Fixed versions: Not specified
e2guardian
Fixed versions: Not specified
e2guardian
Fixed versions: Not specified
e2guardian
Fixed versions: Not specified
e2guardian
Fixed versions: Not specified
e2guardian
Fixed versions: Not specified
e2guardian
Fixed versions: Not specified
Complete source record
{
"id": "a4f2328191b463b4f54421e5ed3b97d03f7354ba716fab00d21194173b1b7e8c",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2021-44273",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2021-44273",
"summary": "e2guardian v5.4.x <= v5.4.3r is affected by missing SSL certificate validation in the SSL MITM engine. In standalone mode (i.e., acting as a proxy or a transparent proxy), with SSL MITM enabled, e2guardian, if built with OpenSSL v1.1.x, did not validate hostnames in certificates of the web servers that it connected to, and thus was itself vulnerable to MITM attacks.",
"evidence": "osv:UBUNTU-CVE-2021-44273",
"products": [
{
"name": {
"value": "e2guardian",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "3.4.0.3-2",
"evidence": "/affected/0/versions"
}
]
},
{
"name": {
"value": "e2guardian",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "5.3.3-1",
"evidence": "/affected/1/versions"
},
{
"value": "5.3.4-1",
"evidence": "/affected/1/versions"
}
]
},
{
"name": {
"value": "e2guardian",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "5.3.4-2",
"evidence": "/affected/2/versions"
},
{
"value": "5.3.5-1",
"evidence": "/affected/2/versions"
},
{
"value": "5.3.5-2",
"evidence": "/affected/2/versions"
},
{
"value": "5.3.5-2build1",
"evidence": "/affected/2/versions"
},
{
"value": "5.3.5-3",
"evidence": "/affected/2/versions"
}
]
},
{
"name": {
"value": "e2guardian",
"evidence": "/affected/3/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "5.3.5-4.1ubuntu1",
"evidence": "/affected/3/versions"
},
{
"value": "5.3.5-6ubuntu1",
"evidence": "/affected/3/versions"
},
{
"value": "5.3.5-6ubuntu2",
"evidence": "/affected/3/versions"
},
{
"value": "5.3.5-6ubuntu3",
"evidence": "/affected/3/versions"
}
]
},
{
"name": {
"value": "e2guardian",
"evidence": "/affected/4/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "5.5.7-1",
"evidence": "/affected/4/versions"
},
{
"value": "5.5.8-1",
"evidence": "/affected/4/versions"
}
]
},
{
"name": {
"value": "e2guardian",
"evidence": "/affected/5/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "5.5.9-2",
"evidence": "/affected/5/versions"
},
{
"value": "5.5.9-2ubuntu1",
"evidence": "/affected/5/versions"
}
]
},
{
"name": {
"value": "e2guardian",
"evidence": "/affected/6/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "5.5.8-1",
"evidence": "/affected/6/versions"
},
{
"value": "5.5.9-2",
"evidence": "/affected/6/versions"
}
]
}
],
"severity": "high",
"structured": {
"id": "UBUNTU-CVE-2021-44273",
"aliases": [
"UBUNTU-CVE-2021-44273"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N"
},
{
"type": "Ubuntu",
"score": "medium"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "e2guardian",
"purl": "pkg:deb/ubuntu/e2guardian?arch=source&distro=bionic",
"ecosystem": "Ubuntu:18.04:LTS"
},
"versions": [
"3.4.0.3-2"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-44273.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "e2guardian",
"binary_version": "3.4.0.3-2"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "e2guardian",
"purl": "pkg:deb/ubuntu/e2guardian?arch=source&distro=focal",
"ecosystem": "Ubuntu:20.04:LTS"
},
"versions": [
"5.3.3-1",
"5.3.4-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-44273.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "e2guardian",
"binary_version": "5.3.4-1"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "e2guardian",
"purl": "pkg:deb/ubuntu/e2guardian?arch=source&distro=jammy",
"ecosystem": "Ubuntu:22.04:LTS"
},
"versions": [
"5.3.4-2",
"5.3.5-1",
"5.3.5-2",
"5.3.5-2build1",
"5.3.5-3"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-44273.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "e2guardian",
"binary_version": "5.3.5-3"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "e2guardian",
"purl": "pkg:deb/ubuntu/e2guardian?arch=source&distro=noble",
"ecosystem": "Ubuntu:24.04:LTS"
},
"versions": [
"5.3.5-4.1ubuntu1",
"5.3.5-6ubuntu1",
"5.3.5-6ubuntu2",
"5.3.5-6ubuntu3"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-44273.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "e2guardian",
"binary_version": "5.3.5-6ubuntu3"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "e2guardian",
"purl": "pkg:deb/ubuntu/e2guardian?arch=source&distro=questing",
"ecosystem": "Ubuntu:25.10"
},
"versions": [
"5.5.7-1",
"5.5.8-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-44273.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "e2guardian",
"binary_version": "5.5.8-1"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "e2guardian",
"purl": "pkg:deb/ubuntu/e2guardian?arch=source&distro=stonking",
"ecosystem": "Ubuntu:26.10"
},
"versions": [
"5.5.9-2",
"5.5.9-2ubuntu1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-44273.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "e2guardian",
"binary_version": "5.5.9-2ubuntu1"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "e2guardian",
"purl": "pkg:deb/ubuntu/e2guardian?arch=source&distro=resolute",
"ecosystem": "Ubuntu:26.04:LTS"
},
"versions": [
"5.5.8-1",
"5.5.9-2"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-44273.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "e2guardian",
"binary_version": "5.5.9-2"
}
]
}
}
],
"modified": "2026-10-17T12:55:55.020814260Z",
"provider": "osv",
"upstream": [
"CVE-2021-44273"
],
"references": [
"https://ubuntu.com/security/CVE-2021-44273",
"https://www.openwall.com/lists/oss-security/2021/12/23/2",
"https://github.com/e2guardian/e2guardian/issues/707",
"https://github.com/e2guardian/e2guardian/commit/eae46a7e2a57103aadca903c4a24cca94dc502a2",
"https://www.cve.org/CVERecord?id=CVE-2021-44273"
]
},
"related_cves": [
{
"value": "CVE-2021-44273",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 354283,
"published_at": "2021-12-23T12:15:00+00:00"
}