ubuntu-cve-2021-36367
Vulnerability from osv_ubuntu
Published
2021-07-09 21:15
Modified
2025-10-24 04:50
Summary
Details

PuTTY through 0.75 proceeds with establishing an SSH session even if it has never sent a substantive authentication response. This makes it easier for an attacker-controlled SSH server to present a later spoofed authentication prompt (that the attacker can use to capture credential data, and use that data for purposes that are undesired by the client user).

Severity
8.1 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
8.1 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
N/A (UNKNOWN)
medium
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "pterm",
            "binary_version": "0.67-3+deb9u1build0.16.04.1"
          },
          {
            "binary_name": "putty",
            "binary_version": "0.67-3+deb9u1build0.16.04.1"
          },
          {
            "binary_name": "putty-tools",
            "binary_version": "0.67-3+deb9u1build0.16.04.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:16.04:LTS",
        "name": "putty",
        "purl": "pkg:deb/ubuntu/putty@0.67-3+deb9u1build0.16.04.1?arch=source\u0026distro=xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.65-2",
        "0.66-1",
        "0.66-2",
        "0.66-3",
        "0.66-4",
        "0.67-1",
        "0.67-2",
        "0.67-3build0.16.04.1",
        "0.67-3+deb9u1build0.16.04.1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "pterm",
            "binary_version": "0.70-4"
          },
          {
            "binary_name": "putty",
            "binary_version": "0.70-4"
          },
          {
            "binary_name": "putty-tools",
            "binary_version": "0.70-4"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:18.04:LTS",
        "name": "putty",
        "purl": "pkg:deb/ubuntu/putty@0.70-4?arch=source\u0026distro=bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.70-1",
        "0.70-2",
        "0.70-3",
        "0.70-4"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "pterm",
            "binary_version": "0.73-2"
          },
          {
            "binary_name": "putty",
            "binary_version": "0.73-2"
          },
          {
            "binary_name": "putty-tools",
            "binary_version": "0.73-2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:20.04:LTS",
        "name": "putty",
        "purl": "pkg:deb/ubuntu/putty@0.73-2?arch=source\u0026distro=focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.72-1",
        "0.73-1",
        "0.73-2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "pterm",
            "binary_version": "0.76-2"
          },
          {
            "binary_name": "putty",
            "binary_version": "0.76-2"
          },
          {
            "binary_name": "putty-tools",
            "binary_version": "0.76-2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "putty",
        "purl": "pkg:deb/ubuntu/putty@0.76-2?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.75-3",
        "0.76-1",
        "0.76-2"
      ]
    }
  ],
  "aliases": [],
  "details": "PuTTY through 0.75 proceeds with establishing an SSH session even if it has never sent a substantive authentication response. This makes it easier for an attacker-controlled SSH server to present a later spoofed authentication prompt (that the attacker can use to capture credential data, and use that data for purposes that are undesired by the client user).",
  "id": "UBUNTU-CVE-2021-36367",
  "modified": "2025-10-24T04:50:26Z",
  "published": "2021-07-09T21:15:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2021-36367"
    },
    {
      "type": "REPORT",
      "url": "https://git.tartarus.org/?p=simon/putty.git;a=commit;h=1dc5659aa62848f0aeb5de7bd3839fecc7debefa"
    },
    {
      "type": "REPORT",
      "url": "https://www.chiark.greenend.org.uk/~sgtatham/putty/changes.html"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2021-36367"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2021-36367"
  ]
}



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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.