USN-8721-1 (UBUNTU-CVE-2026-73281)

Vulnerability from osv_ubuntu – Published: 2026-09-03 12:30 – Updated: 2026-09-03 12:30 – Source website
VLAI
Summary
openssh vulnerabilities
Details

It was discovered that OpenSSH's ssh-agent incorrectly handled interactions between agent locking and the session-bind@openssh.com extension. A remote attacker with access to a forwarded agent connection could possibly use this issue to perform operations that should only be available locally, such as adding tokens or using keys. (CVE-2026-73281)

It was discovered that OpenSSH's ssh client incorrectly handled concurrent remote-forwarding operations. A remote attacker could possibly use this issue to cause a use-after-free condition, resulting in a denial of service or the execution of arbitrary code. (CVE-2026-73282)

It was discovered that OpenSSH's sshd server incorrectly applied the restrict keyword from authorized_keys to tunnel forwarding requests. A local attacker with an authorized key could possibly use this issue to bypass intended tunnel forwarding restrictions. (CVE-2026-73283)

References
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "cves_map": {
          "cves": [
            {
              "id": "CVE-2026-73281",
              "severity": [
                {
                  "score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:N",
                  "type": "CVSS_V3"
                },
                {
                  "score": "medium",
                  "type": "Ubuntu"
                }
              ]
            },
            {
              "id": "CVE-2026-73282",
              "severity": [
                {
                  "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N",
                  "type": "CVSS_V3"
                },
                {
                  "score": "medium",
                  "type": "Ubuntu"
                }
              ]
            },
            {
              "id": "CVE-2026-73283",
              "severity": [
                {
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                  "type": "CVSS_V3"
                },
                {
                  "score": "medium",
                  "type": "Ubuntu"
                }
              ]
            }
          ],
          "ecosystem": "Ubuntu:22.04:LTS"
        }
      },
      "ecosystem_specific": {
        "availability": "No subscription required",
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          },
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          },
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      },
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      },
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        "1:8.9p1-3",
        "1:8.9p1-3ubuntu0.1",
        "1:8.9p1-3ubuntu0.3",
        "1:8.9p1-3ubuntu0.4",
        "1:8.9p1-3ubuntu0.5",
        "1:8.9p1-3ubuntu0.6",
        "1:8.9p1-3ubuntu0.7",
        "1:8.9p1-3ubuntu0.10",
        "1:8.9p1-3ubuntu0.11",
        "1:8.9p1-3ubuntu0.13",
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        "1:8.9p1-3ubuntu0.15",
        "1:8.9p1-3ubuntu0.16"
      ]
    },
    {
      "database_specific": {
        "cves_map": {
          "cves": [
            {
              "id": "CVE-2026-73281",
              "severity": [
                {
                  "score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:N",
                  "type": "CVSS_V3"
                },
                {
                  "score": "medium",
                  "type": "Ubuntu"
                }
              ]
            },
            {
              "id": "CVE-2026-73282",
              "severity": [
                {
                  "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N",
                  "type": "CVSS_V3"
                },
                {
                  "score": "medium",
                  "type": "Ubuntu"
                }
              ]
            },
            {
              "id": "CVE-2026-73283",
              "severity": [
                {
                  "score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N",
                  "type": "CVSS_V3"
                },
                {
                  "score": "medium",
                  "type": "Ubuntu"
                }
              ]
            }
          ],
          "ecosystem": "Ubuntu:24.04:LTS"
        }
      },
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "openssh-client",
            "binary_version": "1:9.6p1-3ubuntu13.19"
          },
          {
            "binary_name": "openssh-server",
            "binary_version": "1:9.6p1-3ubuntu13.19"
          },
          {
            "binary_name": "openssh-sftp-server",
            "binary_version": "1:9.6p1-3ubuntu13.19"
          },
          {
            "binary_name": "openssh-tests",
            "binary_version": "1:9.6p1-3ubuntu13.19"
          },
          {
            "binary_name": "ssh",
            "binary_version": "1:9.6p1-3ubuntu13.19"
          },
          {
            "binary_name": "ssh-askpass-gnome",
            "binary_version": "1:9.6p1-3ubuntu13.19"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "openssh",
        "purl": "pkg:deb/ubuntu/openssh@1:9.6p1-3ubuntu13.19?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1:9.6p1-3ubuntu13.19"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1:9.3p1-1ubuntu3",
        "1:9.4p1-1ubuntu1",
        "1:9.6p1-3ubuntu1",
        "1:9.6p1-3ubuntu2",
        "1:9.6p1-3ubuntu11",
        "1:9.6p1-3ubuntu12",
        "1:9.6p1-3ubuntu13",
        "1:9.6p1-3ubuntu13.3",
        "1:9.6p1-3ubuntu13.4",
        "1:9.6p1-3ubuntu13.5",
        "1:9.6p1-3ubuntu13.7",
        "1:9.6p1-3ubuntu13.8",
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      ]
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    {
      "database_specific": {
        "cves_map": {
          "cves": [
            {
              "id": "CVE-2026-73281",
              "severity": [
                {
                  "score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:N",
                  "type": "CVSS_V3"
                },
                {
                  "score": "medium",
                  "type": "Ubuntu"
                }
              ]
            },
            {
              "id": "CVE-2026-73282",
              "severity": [
                {
                  "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N",
                  "type": "CVSS_V3"
                },
                {
                  "score": "medium",
                  "type": "Ubuntu"
                }
              ]
            },
            {
              "id": "CVE-2026-73283",
              "severity": [
                {
                  "score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N",
                  "type": "CVSS_V3"
                },
                {
                  "score": "medium",
                  "type": "Ubuntu"
                }
              ]
            }
          ],
          "ecosystem": "Ubuntu:26.04:LTS"
        }
      },
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "openssh-client",
            "binary_version": "1:10.2p1-2ubuntu3.6"
          },
          {
            "binary_name": "openssh-client-gssapi",
            "binary_version": "1:10.2p1-2ubuntu3.6"
          },
          {
            "binary_name": "openssh-server",
            "binary_version": "1:10.2p1-2ubuntu3.6"
          },
          {
            "binary_name": "openssh-server-gssapi",
            "binary_version": "1:10.2p1-2ubuntu3.6"
          },
          {
            "binary_name": "openssh-sftp-server",
            "binary_version": "1:10.2p1-2ubuntu3.6"
          },
          {
            "binary_name": "openssh-tests",
            "binary_version": "1:10.2p1-2ubuntu3.6"
          },
          {
            "binary_name": "ssh",
            "binary_version": "1:10.2p1-2ubuntu3.6"
          },
          {
            "binary_name": "ssh-askpass-gnome",
            "binary_version": "1:10.2p1-2ubuntu3.6"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "openssh",
        "purl": "pkg:deb/ubuntu/openssh@1:10.2p1-2ubuntu3.6?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
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            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1:10.0p1-5ubuntu5",
        "1:10.2p1-2ubuntu1",
        "1:10.2p1-2ubuntu3",
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        "1:10.2p1-2ubuntu3.4",
        "1:10.2p1-2ubuntu3.5"
      ]
    }
  ],
  "aliases": [],
  "details": "It was discovered that OpenSSH\u0027s ssh-agent incorrectly handled interactions\nbetween agent locking and the session-bind@openssh.com extension. A remote\nattacker with access to a forwarded agent connection could possibly use\nthis issue to perform operations that should only be available locally,\nsuch as adding tokens or using keys. (CVE-2026-73281)\n\nIt was discovered that OpenSSH\u0027s ssh client incorrectly handled concurrent\nremote-forwarding operations. A remote attacker could possibly use this\nissue to cause a use-after-free condition, resulting in a denial of service\nor the execution of arbitrary code. (CVE-2026-73282)\n\nIt was discovered that OpenSSH\u0027s sshd server incorrectly applied the\nrestrict keyword from authorized_keys to tunnel forwarding requests. A\nlocal attacker with an authorized key could possibly use this issue to\nbypass intended tunnel forwarding restrictions. (CVE-2026-73283)",
  "id": "USN-8721-1",
  "modified": "2026-09-03T12:30:15Z",
  "published": "2026-09-03T12:30:15Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://ubuntu.com/security/notices/USN-8721-1"
    },
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-73281"
    },
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-73282"
    },
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-73283"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "summary": "openssh vulnerabilities",
  "upstream": [
    "UBUNTU-CVE-2026-73281",
    "UBUNTU-CVE-2026-73282",
    "UBUNTU-CVE-2026-73283"
  ]
}



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