openssh — security advisory
An issue was discovered in OpenSSH before 8.9. If a client is using public-key authentication with agent forwarding but without -oLogLevel=verbose, and an attacker has silently modified the server to support the None authentication option, then the user cannot determine whether FIDO authentication is going to confirm that the user wishes to connect to that server, or that the user wishes to allow that server to connect to a different server on the user's behalf. NOTE: the vendor's position is "this is not an authentication bypass, since nothing is being bypassed.
- Products
- openssh
- Affected versions
- Not specified
- Fixed versions
- 1:8.9p1-1
- CVEs
- CVE-2021-36368
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 01:43 UTC · Revision 1
Source evidence
An issue was discovered in OpenSSH before 8.9. If a client is using public-key authentication with agent forwarding but without -oLogLevel=verbose, and an attacker has silently modified the server to support the None authentication option, then the user cannot determine whether FIDO authentication is going to confirm that the user wishes to connect to that server, or that the user wishes to allow that server to connect to a different server on the user's behalf. NOTE: the vendor's position is "this is not an authentication bypass, since nothing is being bypassed.
osv:DEBIAN-CVE-2021-36368
openssh
Fixed versions: 1:8.9p1-1
openssh
Fixed versions: 1:8.9p1-1
openssh
Fixed versions: 1:8.9p1-1
Complete source record
{
"id": "84c832b4470a7b94821f0ba1f8b9cb7e5fa9c7acc911ae091fcc0673aa62905c",
"url": "https://osv.dev/vulnerability/DEBIAN-CVE-2021-36368",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "DEBIAN-CVE-2021-36368",
"summary": "An issue was discovered in OpenSSH before 8.9. If a client is using public-key authentication with agent forwarding but without -oLogLevel=verbose, and an attacker has silently modified the server to support the None authentication option, then the user cannot determine whether FIDO authentication is going to confirm that the user wishes to connect to that server, or that the user wishes to allow that server to connect to a different server on the user's behalf. NOTE: the vendor's position is \"this is not an authentication bypass, since nothing is being bypassed.",
"evidence": "osv:DEBIAN-CVE-2021-36368",
"products": [
{
"name": {
"value": "openssh",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "1:8.9p1-1",
"evidence": "/affected/0/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "openssh",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "1:8.9p1-1",
"evidence": "/affected/1/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "openssh",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "1:8.9p1-1",
"evidence": "/affected/2/ranges"
}
],
"affected_versions": []
}
],
"severity": "low",
"structured": {
"id": "DEBIAN-CVE-2021-36368",
"aliases": [
"DEBIAN-CVE-2021-36368"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1:8.9p1-1"
}
]
}
],
"package": {
"name": "openssh",
"purl": "pkg:deb/debian/openssh?arch=source&distro=bookworm",
"ecosystem": "Debian:12"
},
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2021-36368.json"
},
"ecosystem_specific": {
"urgency": "unimportant"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1:8.9p1-1"
}
]
}
],
"package": {
"name": "openssh",
"purl": "pkg:deb/debian/openssh?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2021-36368.json"
},
"ecosystem_specific": {
"urgency": "unimportant"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1:8.9p1-1"
}
]
}
],
"package": {
"name": "openssh",
"purl": "pkg:deb/debian/openssh?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2021-36368.json"
},
"ecosystem_specific": {
"urgency": "unimportant"
}
}
],
"modified": "2026-10-23T18:04:50.774418002Z",
"provider": "osv",
"upstream": [
"CVE-2021-36368"
],
"references": [
"https://security-tracker.debian.org/tracker/CVE-2021-36368"
]
},
"related_cves": [
{
"value": "CVE-2021-36368",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 424093,
"published_at": "2022-03-13T00:15:07.937+00:00"
}