MediumFix available
dovecot — security advisory
Attacker can use a specially crafted base64 exchange between Dovecot and Client to fake SCRAM TLS channel binding. This requires that the attacker is able to position itself between Dovecot and the client connection. If successful, the attacker can eavesdrop communications between Dovecot and client as MITM proxy. Install fixed version. No publicly available exploits are known.
- Products
- dovecot
- Affected versions
- 1:2.3.19.1+dfsg1-2.1, 1:2.3.19.1+dfsg1-2.1+deb12u1, 1:2.3.19.1+dfsg1-2.1+deb12u2, 1:2.3.19.1+dfsg1-2.1+deb12u3, 1:2.3.19.1+dfsg1-2.1+deb12u4, 1:2.3.19.1+dfsg1-2.1+deb12u5, 1:2.4.1+dfsg1-6, 1:2.4.1+dfsg1-6+deb13u1, 1:2.4.1+dfsg1-6+deb13u2, 1:2.4.1+dfsg1-6+deb13u3, 1:2.4.1+dfsg1-6+deb13u4, 1:2.4.1+dfsg1-6+deb13u5, 1:2.4.1+dfsg1-7, 1:2.4.1+dfsg1-8, 1:2.4.1+dfsg1-9, 1:2.4.2+dfsg1-1, 1:2.4.2+dfsg1-2, 1:2.4.2+dfsg1-3, 1:2.4.2+dfsg1-4, 1:2.4.3+dfsg1-1, 1:2.4.3+dfsg1-2
- Fixed versions
- 1:2.3.19.1+dfsg1-2.1+deb12u6, 1:2.4.1+dfsg1-6+deb13u6, 1:2.4.4+dfsg1-1
- CVEs
- CVE-2026-33603
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 17:48 UTC · Revision 2
Source evidence
Attacker can use a specially crafted base64 exchange between Dovecot and Client to fake SCRAM TLS channel binding. This requires that the attacker is able to position itself between Dovecot and the client connection. If successful, the attacker can eavesdrop communications between Dovecot and client as MITM proxy. Install fixed version. No publicly available exploits are known.
osv:DEBIAN-CVE-2026-33603
dovecot
Fixed versions: 1:2.3.19.1+dfsg1-2.1+deb12u6
dovecot
Fixed versions: 1:2.4.1+dfsg1-6+deb13u6
dovecot
Fixed versions: 1:2.4.4+dfsg1-1
Complete source record
{
"id": "eda6fb846bc8dbfb66ec3c95ea4ee446477565a5f3736d8e4bfc47300282d201",
"url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-33603",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "DEBIAN-CVE-2026-33603",
"summary": "Attacker can use a specially crafted base64 exchange between Dovecot and Client to fake SCRAM TLS channel binding. This requires that the attacker is able to position itself between Dovecot and the client connection. If successful, the attacker can eavesdrop communications between Dovecot and client as MITM proxy. Install fixed version. No publicly available exploits are known.",
"evidence": "osv:DEBIAN-CVE-2026-33603",
"products": [
{
"name": {
"value": "dovecot",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "1:2.3.19.1+dfsg1-2.1+deb12u6",
"evidence": "/affected/0/ranges"
}
],
"affected_versions": [
{
"value": "1:2.3.19.1+dfsg1-2.1",
"evidence": "/affected/0/versions"
},
{
"value": "1:2.3.19.1+dfsg1-2.1+deb12u1",
"evidence": "/affected/0/versions"
},
{
"value": "1:2.3.19.1+dfsg1-2.1+deb12u2",
"evidence": "/affected/0/versions"
},
{
"value": "1:2.3.19.1+dfsg1-2.1+deb12u3",
"evidence": "/affected/0/versions"
},
{
"value": "1:2.3.19.1+dfsg1-2.1+deb12u4",
"evidence": "/affected/0/versions"
},
{
"value": "1:2.3.19.1+dfsg1-2.1+deb12u5",
"evidence": "/affected/0/versions"
}
]
},
{
"name": {
"value": "dovecot",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "1:2.4.1+dfsg1-6+deb13u6",
"evidence": "/affected/1/ranges"
}
],
"affected_versions": [
{
"value": "1:2.4.1+dfsg1-6",
"evidence": "/affected/1/versions"
},
{
"value": "1:2.4.1+dfsg1-6+deb13u1",
"evidence": "/affected/1/versions"
},
{
"value": "1:2.4.1+dfsg1-6+deb13u2",
"evidence": "/affected/1/versions"
},
{
"value": "1:2.4.1+dfsg1-6+deb13u3",
"evidence": "/affected/1/versions"
},
{
"value": "1:2.4.1+dfsg1-6+deb13u4",
"evidence": "/affected/1/versions"
},
{
"value": "1:2.4.1+dfsg1-6+deb13u5",
"evidence": "/affected/1/versions"
}
]
},
{
"name": {
"value": "dovecot",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "1:2.4.4+dfsg1-1",
"evidence": "/affected/2/ranges"
}
],
"affected_versions": [
{
"value": "1:2.4.1+dfsg1-6",
"evidence": "/affected/2/versions"
},
{
"value": "1:2.4.1+dfsg1-7",
"evidence": "/affected/2/versions"
},
{
"value": "1:2.4.1+dfsg1-8",
"evidence": "/affected/2/versions"
},
{
"value": "1:2.4.1+dfsg1-9",
"evidence": "/affected/2/versions"
},
{
"value": "1:2.4.2+dfsg1-1",
"evidence": "/affected/2/versions"
},
{
"value": "1:2.4.2+dfsg1-2",
"evidence": "/affected/2/versions"
},
{
"value": "1:2.4.2+dfsg1-3",
"evidence": "/affected/2/versions"
},
{
"value": "1:2.4.2+dfsg1-4",
"evidence": "/affected/2/versions"
},
{
"value": "1:2.4.3+dfsg1-1",
"evidence": "/affected/2/versions"
},
{
"value": "1:2.4.3+dfsg1-2",
"evidence": "/affected/2/versions"
}
]
}
],
"severity": "medium",
"structured": {
"id": "DEBIAN-CVE-2026-33603",
"aliases": [
"DEBIAN-CVE-2026-33603"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1:2.3.19.1+dfsg1-2.1+deb12u6"
}
]
}
],
"package": {
"name": "dovecot",
"purl": "pkg:deb/debian/dovecot?arch=source&distro=bookworm",
"ecosystem": "Debian:12"
},
"versions": [
"1:2.3.19.1+dfsg1-2.1",
"1:2.3.19.1+dfsg1-2.1+deb12u1",
"1:2.3.19.1+dfsg1-2.1+deb12u2",
"1:2.3.19.1+dfsg1-2.1+deb12u3",
"1:2.3.19.1+dfsg1-2.1+deb12u4",
"1:2.3.19.1+dfsg1-2.1+deb12u5"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-33603.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1:2.4.1+dfsg1-6+deb13u6"
}
]
}
],
"package": {
"name": "dovecot",
"purl": "pkg:deb/debian/dovecot?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"versions": [
"1:2.4.1+dfsg1-6",
"1:2.4.1+dfsg1-6+deb13u1",
"1:2.4.1+dfsg1-6+deb13u2",
"1:2.4.1+dfsg1-6+deb13u3",
"1:2.4.1+dfsg1-6+deb13u4",
"1:2.4.1+dfsg1-6+deb13u5"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-33603.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1:2.4.4+dfsg1-1"
}
]
}
],
"package": {
"name": "dovecot",
"purl": "pkg:deb/debian/dovecot?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"versions": [
"1:2.4.1+dfsg1-6",
"1:2.4.1+dfsg1-7",
"1:2.4.1+dfsg1-8",
"1:2.4.1+dfsg1-9",
"1:2.4.2+dfsg1-1",
"1:2.4.2+dfsg1-2",
"1:2.4.2+dfsg1-3",
"1:2.4.2+dfsg1-4",
"1:2.4.3+dfsg1-1",
"1:2.4.3+dfsg1-2"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-33603.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
],
"modified": "2026-10-27T09:47:39.651397146Z",
"provider": "osv",
"upstream": [
"CVE-2026-33603"
],
"references": [
"https://security-tracker.debian.org/tracker/CVE-2026-33603"
]
},
"related_cves": [
{
"value": "CVE-2026-33603",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 461243,
"published_at": "2026-05-12T14:17:01.6+00:00"
}