UBUNTU-CVE-2026-3706 (CVE-2026-3706)

Vulnerability from osv_ubuntu – Published: 2026-03-08 05:16 – Updated: 2026-09-16 11:31 – Source website
VLAI
Details

A vulnerability was determined in mkj Dropbear up to 2025.89. Impacted is the function unpackneg of the file src/curve25519.c of the component S Range Check. This manipulation causes improper verification of cryptographic signature. The attack can be initiated remotely. The attack is considered to have high complexity. The exploitability is considered difficult. The actual existence of this vulnerability is currently in question. Patch name: fdec3c90a15447bd538641d85e5a3e3ac981011d. To fix this issue, it is recommended to deploy a patch. The project maintainer explains: "Signature Malleability is not exploitable in SSH protocol. (...) [A] PoC doesn't exist for SSH implementation, but rather it's against the internal API."

Severity
3.7 (Low)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
1.7 (Low)
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U
N/A (UNKNOWN)
medium
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "dropbear",
            "binary_version": "2016.72-1"
          },
          {
            "binary_name": "dropbear-bin",
            "binary_version": "2016.72-1"
          },
          {
            "binary_name": "dropbear-initramfs",
            "binary_version": "2016.72-1"
          },
          {
            "binary_name": "dropbear-run",
            "binary_version": "2016.72-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:16.04:LTS",
        "name": "dropbear",
        "purl": "pkg:deb/ubuntu/dropbear@2016.72-1?arch=source\u0026distro=xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2014.65-1ubuntu2",
        "2015.68-1",
        "2015.70-1",
        "2015.71-1",
        "2016.72-1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "dropbear",
            "binary_version": "2017.75-3ubuntu0.1~esm1"
          },
          {
            "binary_name": "dropbear-bin",
            "binary_version": "2017.75-3ubuntu0.1~esm1"
          },
          {
            "binary_name": "dropbear-initramfs",
            "binary_version": "2017.75-3ubuntu0.1~esm1"
          },
          {
            "binary_name": "dropbear-run",
            "binary_version": "2017.75-3ubuntu0.1~esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:18.04:LTS",
        "name": "dropbear",
        "purl": "pkg:deb/ubuntu/dropbear@2017.75-3ubuntu0.1~esm1?arch=source\u0026distro=esm-apps/bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2017.75-2",
        "2017.75-3build1",
        "2017.75-3ubuntu0.1~esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "dropbear",
            "binary_version": "2019.78-2ubuntu0.1~esm1"
          },
          {
            "binary_name": "dropbear-bin",
            "binary_version": "2019.78-2ubuntu0.1~esm1"
          },
          {
            "binary_name": "dropbear-initramfs",
            "binary_version": "2019.78-2ubuntu0.1~esm1"
          },
          {
            "binary_name": "dropbear-run",
            "binary_version": "2019.78-2ubuntu0.1~esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:20.04:LTS",
        "name": "dropbear",
        "purl": "pkg:deb/ubuntu/dropbear@2019.78-2ubuntu0.1~esm1?arch=source\u0026distro=esm-apps/focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2019.78-2build1",
        "2019.78-2ubuntu0.1~esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "dropbear",
            "binary_version": "2020.81-5ubuntu0.1"
          },
          {
            "binary_name": "dropbear-bin",
            "binary_version": "2020.81-5ubuntu0.1"
          },
          {
            "binary_name": "dropbear-initramfs",
            "binary_version": "2020.81-5ubuntu0.1"
          },
          {
            "binary_name": "dropbear-run",
            "binary_version": "2020.81-5ubuntu0.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "dropbear",
        "purl": "pkg:deb/ubuntu/dropbear@2020.81-5ubuntu0.1?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2020.81-3",
        "2020.81-4",
        "2020.81-5",
        "2020.81-5ubuntu0.1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "dropbear",
            "binary_version": "2022.83-4"
          },
          {
            "binary_name": "dropbear-bin",
            "binary_version": "2022.83-4"
          },
          {
            "binary_name": "dropbear-initramfs",
            "binary_version": "2022.83-4"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "dropbear",
        "purl": "pkg:deb/ubuntu/dropbear@2022.83-4?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2022.83-2",
        "2022.83-3",
        "2022.83-4"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "dropbear",
            "binary_version": "2025.88-2"
          },
          {
            "binary_name": "dropbear-bin",
            "binary_version": "2025.88-2"
          },
          {
            "binary_name": "dropbear-initramfs",
            "binary_version": "2025.88-2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:25.10",
        "name": "dropbear",
        "purl": "pkg:deb/ubuntu/dropbear@2025.88-2?arch=source\u0026distro=questing"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2024.86-2",
        "2025.88-2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "dropbear",
            "binary_version": "2025.89-1"
          },
          {
            "binary_name": "dropbear-bin",
            "binary_version": "2025.89-1"
          },
          {
            "binary_name": "dropbear-initramfs",
            "binary_version": "2025.89-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "dropbear",
        "purl": "pkg:deb/ubuntu/dropbear@2025.89-1?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2025.88-2",
        "2025.89-1"
      ]
    }
  ],
  "aliases": [],
  "details": "A vulnerability was determined in mkj Dropbear up to 2025.89. Impacted is the function unpackneg of the file src/curve25519.c of the component S Range Check. This manipulation causes improper verification of cryptographic signature. The attack can be initiated remotely. The attack is considered to have high complexity. The exploitability is considered difficult. The actual existence of this vulnerability is currently in question. Patch name: fdec3c90a15447bd538641d85e5a3e3ac981011d. To fix this issue, it is recommended to deploy a patch. The project maintainer explains: \"Signature Malleability is not exploitable in SSH protocol. (...) [A] PoC doesn\u0027t exist for SSH implementation, but rather it\u0027s against the internal API.\"",
  "id": "UBUNTU-CVE-2026-3706",
  "modified": "2026-09-16T11:31:05Z",
  "published": "2026-03-08T05:16:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-3706"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-3706"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/mkj/dropbear/issues/406"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/mkj/dropbear/pull/407"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/mkj/dropbear/"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/mkj/dropbear/commit/fdec3c90a15447bd538641d85e5a3e3ac981011d"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/mkj/dropbear/issues/406#issue-3978907798"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/str4d/ed25519-java/issues/82#issue-727629226"
    },
    {
      "type": "REPORT",
      "url": "https://vuldb.com/?ctiid.349652"
    },
    {
      "type": "REPORT",
      "url": "https://vuldb.com/?id.349652"
    },
    {
      "type": "REPORT",
      "url": "https://vuldb.com/?submit.765933"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U",
      "type": "CVSS_V4"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-3706"
  ]
}



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