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openssh — security advisory

Type: advisorySources: OSVAdvisory ID: DEBIAN-CVE-2021-36368

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

DEBIAN-CVE-2021-36368

core-osv · Original source

Published 13 Mar 2022, 00:15 UTC

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"
}