ubuntu-cve-2026-3706
Vulnerability from osv_ubuntu
Published
2026-03-08 05:16
Modified
2026-06-24 08:58
Summary
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": "2026-06-24T08:58:39Z",
  "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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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.